ANATOMY or VERTEBRATES. 



43 



m osseous 



total, 17.' In the Conger there are 162 vertebra3 ; in the 

 Ophidium, 204; in the Gynmotus, 236; and even this number 

 is sui-passed in some Plagiostomes. 



Although the vertebras maintain a considerable sameness of 

 form in tlie same fish, they vary much in different species. The 

 bodies are commonly subcylindrical ; as deep, but not so broad, 

 as they arc long ; more or less constricted in the middle, in some 

 to such a degree as to present an hour-glass figure. In Spina- 

 chorhinus they are extremely short; in Fistularia extremely 

 long ; in Tetrodon ^ they are much comjiressed ; in Platycephalus 

 they are more depressed ; in the tail of the Tunny the entire ver- 

 tebra is cubical,' with the ends hollowed as usual, but the four 

 other sides flat, the upper and lower ones being formed, in the 

 connected series, by the neural and ha3mal arches of the vertebra 

 in advance, flattened down and, as it were, pressed into cavities 

 on the upper and under surfaces, of the centrum of the next 

 vertebra ; so that the series is naturally locked together in the 

 dried skeleton ; and these arches cover not the neural and htemal 

 canals of their own, but of the succeeding, centrum. 



The principle of vegetative repetition is manifested, 

 fishes, by the numerous centres of ossification, 

 from which shoot out bony rays affording ad- 

 ditional strength to many of the intermuscular 

 aponeuroses. In this system of bones may 

 be ranked those spines which arc attached to, 

 or near to, the heads of the ribs, and extend 

 upward, outward, and backward, between the 

 dorsal and lateral masses of muscles, fig. 32, i p, 

 fig. 21, pi, a. These 'scleral' spines are 

 termed, according to the vertel^ral element 

 they may adhere to, ' epineurals,' ' epicen- 

 trals,' and ' ei)ipleurals ' ; though each may 

 shift its place, rising or falling gradually along 

 the series of vertebra;. All three kinds are 

 present in the herring, fig. 37, in which n a 

 is the ' ei)ineural,' p a the ' epicentral,' jA a the epipleural spines. 

 The latter have been called ' upper ribs,' and in Polypterus are 

 stronn-er than the ('under') ribs themselves. In Esox and 

 Thymallus the epineural and epicentral spines are present : in 

 Cuprinus the epineural and epipleural ones : in Perca and Gadiis 

 the middle series only is found, passing gradually from the 



Alulnmiiial verfehra, 

 IlL'rring (67"^«'«) 



1 Ostcol. Collection, Mus. Coll. Chir. No. 357, p. SI. 

 "- lb. No. 357. " lb. No. 24-7. xxiv. i, p. 62. 



