256 



LOWER VERTEBRATES. 



liundred heing more or less satisfactorily known. Most of thorn have a stout body 

 diminishing from the head to the tail, but some become quite elongated, and a few- 

 are compressed and oval ; the scales in most have a pectinated hinder margin which 

 is angulated at the middle, whence the stride diverge forwards, but some of the scales 

 are cycloid, and a number have only cycloid scales ; few are entirely naked ; there 

 never is a lateral line ; the head is generally short with bulging cheeks ; the branchial 



Fig. \V,. — l'L,-u,phtl,abi 



apertures are more or less restricted to the sides ; generally, there are two dorsal fins, 

 and in most the first has si.x spines, of which the last is separated by a wider interval 

 than are the others; in some, however, the spines are more numerous, and in others, 

 the fin is continuous with the second; the ventrals are thoracic, and mostly have a 

 spine and five rays, the inner of which are largest ; in most there is also a connectin"- 

 membrane in front between the spine, and behind between the innermost rays, 

 resulting in a funnel-shaped sucker. Finally, a papilla is developed next the anus. 



