PLECTOGNATHI

FAMILY: TETRODONTIDAE

1. DIODON NYCTHEMERUS. Cuv.

Diodon nycthemerus, Cuv., Mém. du Mus., tom. iv , p. 135, pl. 7

A species of Diodon in Mr. Darwin's collection, the number attached to which has been lost, and of which the locality is in consequence unknown, appears referable to the D. nycthemerus of Cuvier.

The spines are long, measuring three quarters of an inch in length; round, sharp, and not very close together. There are five in the front row between the eyes, seven in a transverse row between the pectorals, and ten or eleven between the snout and the dorsal in a longitudinal one: none exactly on the upper part of the tail, but one on each side of the base of it, a little below the termination of the dorsal fin, and a corresponding pair still lower down. The spines on the belly are shorter, and rather closer together than those on the back. One of those on the back in this specimen is accidentally forked.

The true teeth appear on the surface of the jaws like minute scales, as in several species of the genus Scarus.

The fin-ray formula is as follows:

D. 13; A. 13; C. 9; P. 20

Length 5 inches 6 lines

The colours so far as can be judged, the specimen being in spirits and not in very good condition, answer to Cuvier's description of them with tolerable exactness.

 

DIODON RIVULATUS. Cuv.

Diodon rivulatus, Cuv., Mém. du Mus., tom. iv , p. 129, pl. 6.

An individual apparently of this species was picked up by Mr. Darwin on the shore of the Rio Plata at Maldonado. It agrees with Cuvier's description, excepting that the undulating lines are not visible, probably owing to the state of the specimen when found.

The spines are short, barely a quarter of an inch in length, but very strong, compressed, and resembling canine teeth. There are three in the first row between the eyes; about six in a transverse row across the back, and seven or eight in a longitudinal one. Beneath they are shorter and more numerous. The orbits are elevated in ridges, and project forwards over the eyes. Two very small barbules attached to the lower lip. Surface of the jaws smooth, the teeth not appearing as scales.

D. 11; A. 10; C. 8; P. 22

Length 5 inc. 3 lin.

As Cuvier observes, the D. geometricus of Bl. and Schneid.1 approaches very closely this species, and I can hardly think it to be distinct. Yet neither in Mr. Darwin's specimen, which in all other respects agrees exactly with Schneider's figure, do I discern any appearance of the hexagonal meshes on the surface of the body.

1 Syst. Ichth ., pl. 96.

3. DIODON ANTENNATUS. Cuv.?

Diodon antennatus, Cuv., Mém. du Mus., tom. iv , p. 131, pl. 7.

A third species of Diodon , brought home by Mr. Darwin, and taken by him at Bahia, in Brazil, is either the young of the D. antennatus of Cuvier, or else new; but the only individual in the collection is quite small, and not more than an inch in length, excluding caudal. The fleshy filaments above the eyes, which, according to Cuvier, so peculiarly distinguish the D. antennatus, are very distinct - but I see none on the sides. The ground colour would seem darker than he describes, so as to render the spots and markings on the upper parts not distinguishable from it now, if they ever existed. In spirits it appears of a nearly uniform deep brown red. The spines, or rather papillae, are also shorter than represented in his figure; but this may be only the effect of immaturity.

According to Mr. Darwin, the colours when recent were as follows: ‘Above blackish brown, beneath spotted with yellow. Eye with the pupil dark blue; iris yellow, mottled with black.’ It is added: ‘On the head four soft projections; the upper ones longer, like the feelers of a snail.’

Mr. Darwin observes, ‘that the dorsal, caudal, and anal fins, in this species, are so close together that they act as one: these, as well as the pectorals, are in a continued tremulous motion even when the fish is otherwise motionless. The animal propels its body by using the posterior fins in the same manner as a boat is sculled, that is, by moving them rapidly from side to side with an oblique surface exposed to the water. The pectoral fins have great play, which is necessary to enable the animal to swim with its back downwards.’

Mr. Darwin made some further observations on the habits of this species, which have already appeared in his Journal, to which I may refer the reader. 2 The tendency of them is to explain the process by which the water and air are absorbed, when the Diodon distends itself into a spherical form; and to show that the fish can swim, when floating in this state with its back downwards, which Cuvier doubted. He thinks that the water is taken in partly for the sake of regulating its specific gravity. He also notices a curious circumstance with respect to this species, viz., ‘that it emitted from the skin of its belly, when handled, a most beautiful carmine red and fibrous secretion, which permanently stained ivory and paper.’

2 pp. 13, 14.

 

TETRODON AEROSTATICUS. Jen.

T. capite, dorso, lateribus, et pinnâ caudali, nigro-maculatis; ventre turgidissimo, fasciis obliquis nigris: corpore undique muricato, caudâ solum exceptâ: capite brevi; fronte inter oculos paululum depresso: maxillis aequalibus: lineâ laterali nullâ: pinnâ dorsali omnino ante analem positâ: pinnâ caudali subrotundatâ

D. 11; A. 10; C. 10; P. 11

Long. unc. 2. lin. 6

 

Form. Head short. Body approaching to globular, with the skin of the belly extremely loose and capable of great inflation; every where beset with minute prickly asperities, the extreme end of the tail alone excepted. Crown nearly flat, very slightly depressed between the eyes. Jaws equally advanced. Nostrils tubular. No appearance of any lateral line. Dorsal entirely in advance of the anal: both these fins small. Caudal slightly rounded.

Colour. (In spirits.) Head, back, and sides to the depth of the pectorals, greyish brown, spotted with black; the spots very small and crowded on the back, but becoming larger on the flanks and tail. Belly white, with deep black oblique broad bands, inosculating in some places, so as to form large meshes. Dorsal, anal, and pectorals, plain; but the caudal very elegantly and distinctly spotted.

The ticket attached to this specimen has been lost, and its locality is in consequence unknown. In general appearance, it very much resembles the T. lineatus of Bloch , of which it may possibly be a variety; but it would seem to differ from that species, in having the forehead less elevated; in wanting the lateral line altogether, of which I can discover no trace; and in having the whole back and upper part of the sides spotted, and not merely the tail and its fin, as is represented in the T. lineatus.

 

2. TETRODON IMPLUTUS. Jen .

T. sordidč metallico-olivaceus, maculis circularibus albis; ventre albo, lineis olivaceis longitudinalibus, haud admodum turgido: corpore suboblongo, magnâ ex parte laevissimo, ventre solum muricato: maxillis subaequalibus: naribus tubulosis, bifurcatis: lineâ, parum tortuosâ: pinnâ dorsali anali paulo anteriore: pinnâ caudali aequali

D. 10; A. 10; C. 11; P. 16

Long. unc. 4. lin. 9

Form. Approaching to oblong, the belly a little ventricose. Head not so short as in the last species, nor yet much produced. Body every where smooth, excepting the middle of the abdomen from beneath the pectorals to the vent, and not very prickly here. Top of the head slightly depressed between the eyes. Jaws nearly equal; the upper one, if any thing, a very little in advance. Nostrils tubular, the tubes forked from the bottom into two equal branches. The lateral line, which is very distinct, commences behind the mouth, whence it passes under and partly encircles the eye, then arches upwards, making a long sweep, and not descending till it gets above the anal, whence it proceeds nearly along the middle towards the caudal, but loses itself before attaining to that fin. Dorsal fin rather in advance of the anal. Caudal square.

Colour. ‘Dirty metallic olive-green, with white circular spots; belly white, with streaks of the same colour as the back.’ - D. The spots extended on to the basal half of the caudal, but are smaller here than on the body. A white annulus encircles each eye, and a similar one is described round the base of each pectoral. The abdominal streaks run very exactly parallel with the axis of the body, not obliquely as in the last species.

Habitat, Keeling Islands, Indian Ocean.

I can find no species noticed by authors exactly corresponding with the one described above, which was obtained by Mr. Darwin at the Keeling Islands. The form is similar to that of the T. honckenii of Rüppell ,3 but the colours appear different. On the other hand, the marking resemble those of the T. testudineus of Bloch, but that species is rough all over.

3 Surely this cannot be the same as the T. honckenii of Bloch?

 

3. TETRODON ANNULATUS. Jen.

T. dorso et lateribus nigro-fuscis, maculis circularibus atris; infra niveus: corpore oblongo, haud admodum ventricoso, ubique sed parcč muricato, rostro et caudâ exceptis: capite grandiusculo, spatio interoculari lato, parum depresso: maxillis subaequalibus: naribus cylindraceis, recumbentibus, aperturis duabus lateralibus: lineâ laterali in capite tortuosissimâ: pinnâ dorsali vix anali anteriore: pinnâ caudali aequali

D. 8; A. 7; C. 9, etc.; P. 15

Long. unc. 9

Form. Oblong: head rather large; the snout a little more produced than in the last species. Moderately ventricose, and apparently capable of a certain degree of inflation. No where perfectly smooth, except on the snout, tail, and here and there on the flanks; nor very rough, the prickles being minute and rather scattered, most apparent on the back, nape (whence they advance to quite between the eyes), and the middle of the abdomen. The interocular space is broad, equalling two and a half diameters of the eye at least, and a little hollowed out. Jaws are nearly equal, the upper one perhaps a very little in advance. Nostril in the form of a small recumbent cylinder, with an opening at each extremity. Dorsal very little in advance of the anal; the first ray in each of these fins very short. Caudal square.

The lateral line is very tortuous, especially about the head. It commences at the bottom of the gill-cover, whence it ascends vertically behind the eye towards the crown, then passes over the eye towards the snout, descends again beneath the nostril to form a great loop in front of the eye, almost reaching to the corners of the mouth, whence it returns beneath the eye, and crossing its former course nearly at right angles, proceeds along the upper part of the side, getting lower as it approaches beneath the dorsal, to terminate at the caudal. There are also two short transverse lines; one across the snout, connecting the loops; another across the nape, connecting the two main lines after they have assumed the usual direction.

Colour. ‘Beneath snow white. Above dark brownish-black, this colour forming a series of broad oval rings, one within another; the outer and largest ring includes nearly the entire surface of the back and sides. The upper surface is, in addition, marked with round spots of a darker shade. Pectoral and dorsal fins yellowish brown. Iris, inner edge clouded with orange; pupil dark green-blue.’ - D. In its present state, there is no indication of the rings noticed above. The spots, which are small, and cover nearly the whole head, back, and sides, appear also sparingly on the basal half of the caudal, but not on any of the other fins.

Habitat, Galapagos Archipelago.

This species was taken by Mr. Darwin at Chatham Island, in the Galapagos Archipelago. He observes in his notes that it makes a loud grating noise. It is remarkable for the great tortuosity of the lateral line. The form of the nostrils is also rather peculiar.

 

4. TETRODON ANGUSTICEPS. Jen.

PLATE XXVIII

T. supra obscure viridis: capite oblongo, subcompresso, spatio interoculari multum contracto: corpore infra ventricoso, ubique laevissimo, duobus, in summo dorso, cirris cutaneis parvis adornato: maxillis subaequalibus: naribus tubolosis, indivisis, aperturis duâbus lateralibus: lineâ laterali in capite tortuosissimâ: pinnâ dorsali omnino ante pinnam analem; caudali aequali

D. 8; A. 7; C. 9; P. 15

Long. unc. 9. lin. 3

Form. Rather more elongated than the last species; especially in regard to the head, which is also more compressed upwards, reducing the space between the eyes to a narrow channel, much hollowed out, and not exceeding one diameter of the eye. Body inflatable, every where quite smooth. Jaws nearly equal, the upper one perhaps a very little in advance. Nostrils tubular, with two lateral apertures, somewhat similar to those of the last species, but more elevated. Lateral line similar, taking the same windings on the head. A little behind the transverse line on the nape, and nearly above the attachment of the pectoral, are two small skinny appendages: there is also a very minute one on each side of the tail, but none elsewhere. Dorsal wholly before the anal. Caudal square.

Colour. ‘Above dull green: base of the pectorals and dorsal black; a white patch beneath the pectorals.’ - D. The colours must have very much altered from the action of the spirit, as it now appears of a nearly uniform reddish brown, only paler beneath.

Habitat, Galapagos Archipelago.

Another apparently undescribed species of this genus, taken by Mr. Darwin at the same place as the last. He observes in his notes that it is inflatable.


 

 

FAMILY: BALISTIDAE

1. BALISTES VETULA. Bl.

Balistes vetula, Bloch, Ichth., tab. 150.
Balistes vetula, Duperrey (Voyage) Zoologie , p. 114, pl. 9, fig. 2.

Form. Body deep, subrhombic, very much compressed; the greatest depth equalling half the entire length. Tail unarmed. Three of four larger scales than the others behind the branchial orifice. Pelvic bone projecting, prickly, connected with which is a fin consisting of about nine pairs of short rays. Above this fin, and parallel to its base, are two or three rows of short spines, but not much developed. First dorsal of three spines, commencing above the pectoral; first spine very strong and rough, the third not much smaller than the second. Second dorsal, and anal, which answer to each other, nearly even throughout, the anterior rays not being prolonged beyond the others. The caudal is injured, and its exact form cannot be determined. No lateral line.

D. 3-30; A. 27; C. 12; P. 14

Length 1 inc. 10 lin.

Colour. (In spirits.) Yellowish trey, becoming paler beneath. Three or four dark transverse streaks across the head from eye to eye: beneath the eye one or two indistinct streaks, passing off towards the branchial orifice: also two very distinct longer ones commencing on the upper part of the snout before the eyes, and passing obliquely across the cheeks towards the roots of the pectorals, parallel to those last mentioned. Besides the above, there are several obliquely transverse interrupted lines on the sides of the body: in one specimen, these lines are not well defined; in another, they are distinct, but so much interrupted as to have the appearance of spots arranged in a linear series. Two or three transverse lines encircling the tail; and some remains of longitudinal stripes on the second dorsal and anal fins.

The above description is that of two very small specimens of a species of Balistes taken by Mr. Darwin in Lat. 14° 20` South, Long. 38° 8` West, about sixty-five miles from land. I have very little doubt of their being the young of the B. vetula of Bloch . The only respects in which they appear to differ from that species are the oblique lines on the back being carried completely across the sides in the form of lines of spots, and the anterior portions of the second dorsal and anal fins not being prolonged in a point; but both these differences may be the effect of immaturity.

 

2. BALISTES ACULEATUS. Bl.

Balistes aculeatus, Bloch, Ichth., tab. 149.
Balistes aculeatus, Benn. in Zool. of Beechey's Voy ., p. 69, pl. 22, f. 2.

Form. Body deep, subrhombic. Tail armed with three rows of prickles, eleven in the uppermost row, about nine or ten in the middle one, and five or six in the lowermost. A few larger scales than the others behind the branchial orifice. Pelvic bone very rough and prickly, the spines that follow short, and not protruding much beyond the skin. First spine in the dorsal very strong, aculeated at the anterior edge, but not at the sides; no third spine in this fin. Second dorsal and anal even. Caudal rounded.

D. 2-24; A. 21; C. 12; P. 13

Length 2 inc. 3 lin.

Colour. Not noticed in the recent state. The ground colour has probably been altered by the spirit, but the markings are still very distinct, and accord tolerably with Bloch's figure, except that the oblique bands on the posterior part of the body, in front of and above the anal, are darker; while they alternate with four white ones, which are particularly conspicuous. Possibly these white bands may have been originally blue, as the narrow stripes descending from the eyes to the pectorals, which evidently were of that colour, are nearly faded to a white. There is also a white stain on each side of the tail, where the spines are, which appears to have been blue originally: the spines themselves are deep shining black.

This specimen shows the black transverse bands between the eyes, and the broad band passing from the eye to the pectoral, between the narrow blue ones above alluded to, all represented by Bloch, but not observed by Mr. Bennett in the specimen figured in the Zoology of Beechey's Voyage .

Habitat, Tahiti.

The above specimen was taken by Mr. Darwin at Tahiti. It is quite small, and differs in some respects from the figures of Bloch and other authors, but it is evidently referable to the B. aculeatus. The species is probably subject to variation in respect of colouring.

 

1. ALEUTERES MACULOSUS. Richards.

Aleuteres maculosus, Richards. in Proceed. of Zool. Soc., 1840, p. 28.

Form. Oval, somewhat approaching to fusiform behind, very much compressed. The greatest depth one-third of the entire length. Skin covered with little granular points, terminating in very minute bristles, and communicating a slight roughness to the touch, when the finger is passed from tail to head. Snout rather prominent and acute: jaws equal. Dorsal spine springing from above the middle of the orbit of the eye; strong, with four rows of sharp prickles at the four angles, pointing downwards, and very regularly set: second dorsal spine very minute. The second dorsal and anal fins have been lost in this specimen, and their form and number of rays cannot be determined. The pectorals are small, each with twelve rays. Caudal rounded, also with twelve rays.

Length 5 inc. 4 lines

Colour. ‘Mottled with pale blackish green, leaving white spots.’ - D. In its present state, the skin is nearly gone from long maceration in impure spirit: such portions as are left accord well with Dr. Richardson's description, appearing of a mouse-grey, with darker mottlings. There are three or four rather indistinct dark fasciae across the caudal.

Habitat, King George's Sound.

I have scarcely any doubt of this being the A. maculosus described by Dr. Richardson, in his recently published notes on a collection of fishes from Van Diemen's Land. Mr. Darwin's specimen, which is in bad condition, was obtained by him in King George's Sound.

 

2. ALEUTERES VELUTINUS. Jen.

A. pallide fuscescens, fasciis quatuor obscurioribus, longitudinalibus, indistinctis; pinnis pallidae aurantiis: corpore oblongo-ovali elongato; cute delicate hispidâ, scabrâ: rostro producto, apice obtuso: spinâ dorsali aculeis lateralibus deflexis, uniseriatis: pinnis dorsali secundâ et anali multum ante caudalem desinentibus

D. 2-33; A. 31; C. 12; P. 13 vel 14

Long. unc. 8

Form. Elongated, approaching to oblong-oval, the tail rather slender. Greatest depth exactly one-fourth of the entire length, and equalling the length of the head, this last being measured to the upper angle of the oblique branchial orifice. Back slightly arched, the curvature rather exceeding that of the belly. Profile in front of the dorsal spine falling very gradually, and not much out of the rectilineal. Snout considerably produced, but blunt at the extremity. Mouth small; jaws equal; teeth strong, and very sharp. Eyes round, placed exactly above the branchial orifice. The grains on the skin are coarser than in the A. maculosus, and the bristles springing from them longer and more developed, especially on the posterior part of the body, communicating a harsher feel to the touch: these bristles are slightly hooked at their extremities, the tips being turned towards the tail.

Dorsal spine strong, situate above the posterior part of the orbit, with only two principal rows of prickles, one on each of the two lateral edges; anteriorly granulated at bottom, with a few rudimentary prickles towards the apex, but posteriorly almost quite smooth. Second spine very minute. The distance from the first spine to the commencement of the second dorsal fin equals twice the length of that spine. The anal commences under the fifth dorsal ray, and ends nearly in a line with the termination of that fin, but extends a trifle further. Both fins fall short of the caudal by a considerable space. Pectorals rather small. The caudal is worn at the end, but appears to have been either square or slightly rounded.

Colour. ‘Very pale brown; fins pale orange.’ - D.

A second specimen is smaller than the above, measuring six inches and three-quarters in length. It is exactly similar in respect to form, and general colour; but the sides are marked with four tolerably distinct longitudinal bands, extending form the branchial orifice to the caudal, rather darker than the ground on which they are traced. There is very little indication of these bands in the first specimen.

Habitat, King George's Sound.

This species was taken by Mr. Darwin in King George's Sound, and appears to be new. It has some points of resemblance with the Balistes ayraud of Quoy and Gaimard but in that the dorsal fin is said to extend to the caudal,4 which is far from being the case here. I have named it velutinus, in respect of the minute bristles which cover the skin, somewhat resembling the pile of velvet.

4 This character, though mentioned in the description, is not, however, represented in the figure. See Freycinet's Voyage (Zoologie), pl. 47, f. 2.

 

OSTRACION PUNCTATUS. Schn.

L'Ostracion pointillé, Lacép., Hist. Nat. des Poiss., tom. i , p. 455, pl. 21, fig. 1.
Ostracion punctatus, Schneid., Syst. Ichth., p. 501.
Ostracon meleagris, Shaw, Nat. Misc., pl. 253.

This well-marked species of Ostracion, first described by Lacépčde from Commerson's MSS., and afterwards figured by Shaw, in his Naturalist's Miscellany, under the name of O. meleagris , was obtained by Mr. Darwin at Tahiti, where it had been previously observed by Captain Cook.

There are two specimens in the collection, both exactly similar, and of the same size, measuring a trifle more than three inches and a half in length. They also accord well with Shaw's figure. Lacépčde, in his description, speaks of the anal fin as being more extended than the dorsal, and as having eleven rays; but in both Mr. Darwin's specimens, I find the number of rays in these two fins the same. The formula is as follows:

D. 9; A. 9; C. 8; P. 10

Schneider has noticed this species twice; first under the name of lentiginosus, and again under that of punctatus.

 

 

CYCLOSTOMI

FAMILY: PETROMYZONIDAE

MYXINE AUSTRALIS. Jen.

Form. Scarcely differing from the M. glutinosa, but apparently rather more slender in proportion to its length. Mouth and cirriform appendages the same. Branchial orifices two, very near together, placed beneath, at a little beyond one-fourth of the entire length. A very conspicuous row of pores along each side of the abdomen. The tail seems somewhat sharper than in the M. glutinosa, and the rays of the low fin which turns round its extremity rather more distinct. Vent distant from the end of the tail rather less than one-eighth of the entire length.

Length 11 inc. 6 lin.

Colour. ‘Above coloured like an earth-worm, but more leaden; beneath yellowish; head purplish.’ - D.

Habitat, Tierra del Fuego.

Mr. Darwin obtained this species by hook amongst the kelp, in Goree Sound, and other parts of Tierra del Fuego, where he observes it is abundant amongst the rocky islets. Its extreme southern locality would suggest the idea of its being distinct from the M. glutinosa of the northern seas; yet the differences between the two, upon comparison, are very slight, and, if it really be so, as I have ventured to consider it, it requires an examination of more specimens to lay down its exact specific character.

Mr. Darwin has made some interesting remarks on the habits of this fish. He observes that it is ‘very vivacious, and retained its life for a long time; that it had great powers of twisting itself, and could swim tail first. When irritated, it struck at any object with its teeth; and by protruding them, in its manner, much resembled an adder striking with its fangs. It vomited up a Sipunculus when caught.’ He adds, that he ‘observed a milky fluid transuding through the row of lateral pores.’