44 



ANATOMY OF VERTEBRATES. 



par- to the pleur-apophyses : in Salmo only the upper series 

 exists, developed from the second to the antepenultimate abdo- 

 minal neurapophysis, in S. Eriox. 1 There are, however, gristly 

 representatives of epipleurals. In Gtyphysodon the epipleurals 

 are anchylosed to the ribs, foreshowing their normal condition 

 in the bird's thorax. According to the seat of their develope- 

 ment they belong to the ( scleroskeleton : ' by their attachments 

 to bone they are ( vertebral appendages.' 



The vertical folds of skin from the middle line, constituting 

 the azygos fins, are the seat of ossifications in most fishes, develop- 

 ing a second row of spines, figs. 34, 38, dn, dn, above the neural, 

 n, and a corresponding row, dh, dk, below the haemal, h, spines. 

 Some of these dermal bones, in certain fishes, project as hard 

 enamelled weapons from the surface of the body. From the 

 bases of the dermal spines, other spines (fig 34, in, Hi) usually 

 shoot downward into the intervals of the neural and haemal spines. 

 In deep-bodied fishes they are broad and strong, as e. g. in the 

 Cock-fish, fig. 38 ; in the flat-fishes they are double, figs. 39 and 

 40 ; and these modifications are usually repeated above and 

 below. Both interneural and interha3inal spines are commonly 

 shaped like daggers, plunged in the flesh to the hilt, which is re- 



38 



Aryyrciosus seiipinnis 



presented by the part to which the fin-ray (dermoneural or 

 dermohamial spine) is attached. In the plaice tribe (Pleuro- 

 nectidce) these superadded dermal ossifications are developed 

 above the cranial as well as the corporal vertebra? (fig. 39, dn), 



1 XLIV. i, p. 16. CLIII. 



