ANATOMY OF VERTEBRATES. 43 



total, 17. l In the Conger there are 162 vertebrae; in the 

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

 is surpassed in some Plagiostomes. 



Although the vertebra? maintain a considerable sameness of 

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

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

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

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

 chorhmus they are extremely short; in Fistularia extremely 

 long ; in Tetrodon 2 they are much compressed ; in Platycephalus 

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

 tebra is cubical, 3 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 haemal 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 iu the 

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

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



The principle of vegetative repetition is manifested, in osseous 

 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 are 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 t 

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

 termed, according to the vertebral element 

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

 trals,' and ' epipleurals ' ; though each may 

 shift its place, rising or falling gradually along 

 the series of vertebra?. All three kinds are Abdominal vertebra, 



a 



Herring (Clupea) 



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

 is the ' epineural,' p a the ' epicentral,' pi a the epipleural spines. 

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

 stronger than the ('under') ribs themselves. In Esox and 

 Thymallus the epineural and epicentral spines are present : in 

 Cyprinus the epineural and epipleural ones : in Perca and Gadus 

 the middle series only is found, passing gradually from the 



1 Osteol. Collection, Mus. Coll. Chir. No. 357, p. 81. 



2 lb. No. 357. 3 lb. No. 247. xliv. i, p. 62. 



