314 



ICHTHYOLOGY. 



spines over the eyes, and on the angles of the body. 2. Some have 

 spines on the end of the ventral edges only. 3. Some have spines 

 over the eyes, and on the edges of the belly. 4. Lastly, in some 

 the body is almost three-edged owing to the gable-formed elevation 

 of the back. Six species. 



Genus IV. Akac.\na, Dr Gray. {Acarana and Platycanthus^ 

 Swain.) Roundish compressed bodies, witb a short tail, which is 

 encompassed by bony plates or rings. 



Sub-Genus I. Aracana, Gray. Having three pairs of flat com- 

 pressed spines on the dorsal aspect (viz., one over each eye, and two 

 pairs on the edge of the rounded back) ; one spine on the side, and 

 two or three on the edge of the compressed belly. Six species. 



Sub-Ocnus II. Caproputjia, Kaup. Back and belly elevated in 

 the middle ; a pair of flat pointed spines on the line which in- 

 closes the back ; another pair on the border of the belly before the 

 anal. The dermal plates very rough, with small radiating tubercles. 

 One species, A. unit^triata, 



Siib-Oenus III. Kentrocapros, Kaup. No orbital spines; back 

 concave, with two flat pointed spines on tlie middle of the dorsal 

 border ; border of the belly rough and denticulated with one spine. 

 One species, A. hcxagona. 



Sub-Genus IV. Anuplocapros, Kaup. No trace of spines on the 

 orbit. Body compressed, and acutely sloped on the back and belly. 

 No spines developed on the borders of the back or belly. One 

 species, A. lenticularis. 



Genus V. C'entadrds, Kaup. A large rough tapering acute 

 spine, standing forwards before the large eye ; a still longer one 

 pointing backwards from the end of the cuirass over the caudal, 

 replacing the second dorsal. Two projections from the border of 

 the back laterally ; four from the border of the belly. One species. 

 V. boops, South Shetland, fig 18. 



II. Head oblong. 



1. The sides only smooth. 



2. Back and sides smooth ; 

 III. Back keeled. 



the belly alone rough. 



Classifica- 

 tion — 

 Lopho- 

 branchs. 



JliiUer has proposed the following sub-genera : — 



Sub-Genus 1. I'liysogaster, MiiU. In the nasal depression a hol- 

 low papilla, with a nostril that is not lengthened out into a tube. 

 A dermal keel on the side of the belly from the throat to the tail. 

 T. oblonguSy lunaris. 



Sub-Genus II. Chelonodon, Jliill. JVo trace o/ a nostril, but in place 

 of it a skinny funnel-shaped tentacle. 



Sub-Geuus III. CkeiUchthys, MiiU. A shorter or longer nostril- 

 tube, and no ventral keel. 



Sub-Gams IV. Arothron, Miill. On each side of the nose solid 

 tentacles, on which the olfactory nerve is expended ; also a musculai- 

 ring round the eye, and a kind of eyelid. 



SUB-FAMILY in. — OKTHAGORISCINI. 



Genus I. Orthagobiscus, Schneid. (Cephahis, Shaw. Sun- 

 fish.) Jaws of Diodon. Body compressed, generally destitute of 

 spines and incapable of inflation, and with the tail so short and 

 high that the tish appears as if its hinder parts were sliced off. 

 Dorsal and anal both high and pointed, and joined to the caudal. 

 No air-bladder ; stomach small, entered directly by the bile-duct. 

 A gelatinous layer immediately under the skin. The abbreviation 

 of the tail is accompanied by a very reduced myelon, looking like 

 a mere ganglionic process of the brain. 0. s2nnosus has pointed 

 tubercles on the body. 



Family lit.— DIODONTIDtE. 



Gymnodontes, Cuv., Miill. Upper and under jaws with which 

 the teeth are incorporated, without a mesial division, resembling 

 the beak of a parrot ; behind the jaw is transversely forked. Skin 

 wholly armed with spines of greater or smaller size. The Diodons 

 and most of the Trti-aodons have the power of inflation. 



SUB-FAMILY I. DIODONTINI. 



Genus I. Diodon. Linn. One nostril at the base of a leaf-like 

 cutaneous process, and the other at the point of the same. Spines 

 subulate, long, thin, and sharp pointed, with two radical processes, 

 and capable of erection or depression. Nine species. 



Genus II. Dicotylichthys, Kaup. Each tentacle two-lobed. 

 No nostril. Spines with three radical processes, which prevent 

 motion ; in the middle of the forehead a spine with two processes. 

 One species, D. punctulatus. 



Genus III. Cyclichthys, Kaup. Two nostrils, one at the base 

 of a tentacle, the other at its point. Spines with three fully de- 

 veloped radical processes, which prevent all motion. Two species. 



Genus IV. L'yaniciithys, Kaup. Nostrils squeezed together 

 on the forehead in a leaf-like tentacle ; one aperture on the inner 

 border next the forehead ; the other one, which is scarcely percep- 

 tible, on the border next the eye. Forehead concave, without a 

 spine in the middle. Body armed with short immoveable spines. 

 One species, 0. cc^ruleits. New Guinea. 



Genus V. Chilomycterus, Bibr. (Wiegm. .i4rcA. 1847.) Nos- 

 trils at the extremity of an extended tentacle. Three large radical 

 processes to the immoveable spines. Body flat. In most instances a 

 spine on the forehead, and two or three above the eyes. Three 

 species. 



SUB-FAMILY II. TETEAODONTINI. 



Tetraodon, Linn., Cuv. Upper and under jaws divided by a me- 

 sial suture, so that they ajjpear to have two teeth above and two 

 below. Spines of the skin much shorter than those of Diodon. 

 The head and tail are generally smooth, but the rest of the body 

 is, with a few exceptions, rendered rough by the presence of minute 

 s})ines. A species which possesses electric powers is destitute of 

 spines, in obedience to a law ascertained by observation, that none 

 of the electric fishes possess scales or spines. 



The following groups are indicated in the Regne Animal, and are 

 likely to receive generic names from the first ichthyologist who 

 publishes descriptions of all the species. 



Genus I. Tetraodon, Cuv. 

 I. Head short, body iiiflatible. 



1. Body rough throughout. 



2. Body smooth throughout. 



3. The sides only smooth ; lateral tubercles. 



4. The sides smooth ; no lateral tubercles. 



fan 



LOPHOBRANCHS. 



Fishes of tills order possess an osseous skeleton, and 

 complete and free jaws, but the ultimate divisions of their 

 branchiae, instead of being pectinated, are divided into small 

 tufts, which are ranged by pairs along the branchial arches. 

 The armour in which these fishes are mailed up, their want 

 of flesh, and their generally angular forms, give them a 

 peculiar aspect. The tubular elongated snout is formed 

 by the nasal, vomer, tympanals, preopercula, and sub- 

 opercula. The nasal bone is a short compressed vertical 

 plate. 



Notwithstanding the odd and stiff appearance of many of 

 the Sea-horse Fish and other small members of this order, 

 some liave prehensile tails {Hippocampus), like those of an 

 American monkey (Cebiis), and when ke|)t in vases 

 nished with slender twigs, to which they can suspend the 

 selves, they form pleasing objects of study. The Hij 

 campi resemble the Chameleon, in being able to direct one 

 eye backwards and the other forwards, and Professor Lich- 

 tenstein observed a circular movement in the water near their 

 gill-openings ; on the right side the whirl revolved to the 

 left, and on the left side to the right, the rotation being 

 symmetrical and constant, like that of a Hotifer. The 

 Hippocampi inhabit all parts of the ocean. Others of the 

 order are remarkable for the singularity of their shapes, or 

 of their cutaneous appendages, or for the brilliancy of their 

 colours. The PhijUopUryx foliatiis, from the seas betw een 

 Australia and New Guinea, yields to no fish in the intensity 

 of its red and purple tints, and in the variety of the leaf- 

 like lappets that adorn it. A very beautiful drawing, by 

 Bauer, of the recent fish taken on Flinders' voyage is in 

 the possession of Mr Brown. 



The most interesting peculiarity, however, in the eco- 

 nomy of the Pipe-fishes is that of the males of most 

 species carrying the eggs about with them until they are 

 hatched. Dr Kaup considers that they show an analogy 

 in this respect to the Marsupials, or the Wandering Pen- 

 guin {Aptenodi/tes Patayonicus), which transports its soli- 

 tary egg in a fold of its skin. In some the egg-pouches 

 are on the breast or belly, in others on the tail, or the eggs 

 are merely glued on in rows, and not covered in by mem- 

 brane. 



