FISH IN GENERAL. 61 



only one bone : the latter consisting of three pieces on each 

 side (No. 62) under the last superior arches, are commonly 

 in the form of a plate, and form the roof of the pharynx. The 

 pharyngeal and branchial apparatus contain usually thirty-six 

 principal pieces, independent of others smaller, arming the 

 interior of the arches, which would amount to more than one 

 hundred. 



The vertebrae of fishes are distinguished by the conical 

 hollow on each of their faces. The double hollow cones 

 which are thus formed in the interval between two vertebrae, 

 are filled by a soft membranous and gelatinous substance, 

 which passes from one void to another by means of an 

 opening through each vertebra, nearly always in the centre, 

 and forms a kind of gelatinous chaplet through the whole. 

 They have, as in other animals, in their superior part, and 

 for the passage of the spinal marrow, an annular portion, 

 above which there is generally a spinous process (c. c. c), 

 and before and behind its basis smaller processes, repre- 

 senting the articular processes in other vertebrated animals ; 

 but they are often incompletely soldered, and scarcely arti- 

 culated. The vertebra? above the abdomen (No. 67, 67) have 

 transverse processes {a. a.) : those further back (No. 68, 68) 

 have those transverse processes turned down and prolonged, 

 often united below by joining pieces, and forming rings 

 (No. 69, 69), protecting a kind of channel which contains the 

 vessels. The vertebrae nearer the tail gradually shorten their 

 processes, and the channel closes. The last united with the 

 interspinous bones form the triangular surface placed ver- 

 tically (No. 70), at the end of which the caudal rays (No. 71) 

 are attached. The number, however, of vertebrae, their 

 length, and other particularities, are infinitely varied. It will 

 be sufficient to add, that their number is not always in pro- 

 portion to the length of the fish. 



The ribs (No. 72, 72) have in general only one head, and 



