ICHTHYOLOGY. 



207 



Introduc- Leptocephali (fig. 4). Totally opposed to these is the Flounder femily we have nearly the same external form Introduc- 



produced by compression, and that lateral dissimilarity al- ''"■'• 

 ready alluded to. Other forms, curious fi'om their gro- ^^-^^s/-^ 



Fi?. 4. 

 Trachvpterus falx , an example of the tliin elongated Tanioidei or Riband- 

 fish family— the O-t/mnetrid/x of our table. 



square box-like shape of the cubical Ostracions (fig. 5), the 

 pyramidal form of others of that tribe, or the round bladder- 

 like figure of the inflated Diodons or the hard-scaled 

 spheroid 3Io»ocentris. We 

 liave examples of a slender 

 elongated cylindrical form ^- 

 among the SyngiiatliidcE 

 or Pipe fish, and among 

 the Eels (fig. 6), Lam- 

 preys, and Sharks. Indeed, 

 the vermiform type exhi- 

 bited by embryos of verte- 

 brals in their earliest stage, 

 is persistent in many fishes, 

 which by the assemblage 

 of other points of their 

 structure enter totally different groups. 



Fig. 5. 



CentnMrw5 6oo/>sof the Ostraciomd<:E dis- 

 covered on Sir JamesClark Ross's me- 

 morable voyage to the Antarctic seas. 



A depressed, dis- 



Fig. 6. 

 Clianno-murccna vittata of the Muraenoid family of Apodals. In thia genus 

 there are no fins, except a slight vestige of rudimentary rays at the end of 

 the tail lying in the thick skin. 



Fig. 7. 

 Kaia I.empnn-i,a Skate from Aoatralii 



Patcccus fronto, one of the many singular forms which the Lophiida exhibit. U^^j' ■ AY'^'f^'^ '"' 

 ]t was discovered by Governor Sir Georce Grey in South Australia. The 

 generic name has reference to the tigure-head of an ancient ship. 



tesqueness, or from the redundancy of certain parts, are not 

 uncommon ; and we need not adduce other examples than 

 those which exist among the Lophiidce, Gobiidce (fig. 8), 



coid shape, with the appendage of a whip-like tail, is com- 

 mon among the Rays (fig. 7) and their allies ; and in the 



Fig. 9. 



Choridactylus mnliiharbus, a member of the Apistes group among the Sclero- 

 genidcc. and furnished like the other Apistes with a treacherous spine on 

 the preorbitar scale bone. The free rays of the pectoral fin are organs of 

 touch analoirous to fingers, and similar to the free rays of the Gurnards, 

 and many other fish that habitually frequent the bottom of the sea. 



Pristida, Sclerogenida (fig. 9), Silurida, or Acantlmrida. 

 Some of the forms which we have thus noticed in general 

 terms, and others which the woodcuts exhibit, are ill calcu- 

 lated for swift progression, and the small and delicate fins 

 of the Ostracions, for instance, can serve little more than 

 the office of rudders to the inflexible scaly case from which 

 they protrude. The chief organs of locomotion in the rapid 

 swimming fish is the tail, which, in a majority of such fish, 

 equals or far exceeds the trunk in length. It sculls a fish 

 along like an oar worked at the stern of a boat. In the ver- 

 miform apodal fishes, and in many Cartilaginei, swift; motion 

 is produced by lateral undulatory strokes of the entire body 

 and tail. When the body is suspended in an element of 

 the same or nearly the same specific gravity with itself, it 

 is moveable by a slight impulse ; and we find, accordingly, 

 that if the limbs exist, they are more tender than the an- 

 alogous members of the higher classes, and that the want 

 of one or both pairs is more common than in other classes. 

 Before we enter on the consideration of the proper ver- 

 tebral skeleton, it may be well to premise that the bones, 

 or hard parts of fishes, are primarily divisible into those of 

 the — 1. Neuro-skeleton or endo-vertebral series; 2. The 

 Splanchno-skeleton, for the special protection of certain or- 

 gans ; 3. DeTtno-skeleton, parts, as the name denotes, of the 

 cutaneous system, and analogous to the exterior skeletons 

 of the lower divisions of animals. 



SECTION m. — THE OSTEOLOGY OF FISHES. 



The structure and growth of bone have been described 

 elsewhere ; and it is sufficient to say here that it consists of 

 animal matter, with diffused earthy particles, chiefly of 



