390 Analytical Synopsis of the Order of Squali. 



19. — In a " Catalogue of the Fishes of tlie Eastern Coast of 

 North America,'' the present author adopted the order of Plagio- 

 stomi entire, and proposed to subdivide it into four sub-orders — 

 Squali, Rhinre, Pristes, and llai£e, thus essentially preserving the 

 an-angement of Cuvier b}' raising his four great genera to sub- 

 ordinal rank and considering his sub-genera as families. But 

 the sub-orders thus constituted are of very unequal value, as the 

 differences existing between the first and the last pairs are of 

 much greater importance than those between the two of each 

 respective pair. I am also convinced that the Pristoidce cannot 

 be separated from the Rhinobatoidse, but must be retained in 

 the same sub-order, and that if there should be any distinction 

 of sub-orders, it cannot be that of Pristes and Raiae. The former 

 may be, indeed, almost said to be Rhinobatoidse with a saw- 

 like snout, and the presence or absence of the ensiform append- 

 age is surely insufficient to designate sub- orders. 



§11. 

 ON THE RELATIONS OF THE ORDER. 



The principal features by which the Sharks are distinguished • 

 from the Rays, are the position of the branchial apertures on 

 the side of the neck, the incomplete scapular arch, and the 

 absence of naso-pectoral cartilages. 



Other peculiar characters, more or less general, are the sub- 

 fusiform or sub-cylindrical shape of the body ; the abrupt flex- 

 ion of the caudal portion of the vertebral column upwards, and 

 the consequent heterocercal condition of the fin ; the very 

 convex outline of the cleft of the mouth ; the well developed 

 teeth ; and the presence of an anal fin. 



An example of the ordinary squaloid form is found in the 

 'common blue sharks, or species of the Cuvierian genus Carcha- 

 rias. In them, the caudal portion of the vertebral column is 



