SQUALID-Ex-— UNCERTAIN TYPES. 317 



a dimple at the root of the tail ; the upper lobe of 

 the caudal elongated^ with two incisions."* 



Oxyrhina Agass. " Teeth long and thick^ li^e nails^ 

 without lateral denticles^ the anterior ones intro- 

 verted ; third tooth in the upper jaw small and short; 

 spiracles small." 



Rhiniodon Smith. " Spiracles small; mouth on the 

 top of the snout." — N. B. This^ which is evidently 

 a chironectiform type, is placed by MM. Miiller 

 and Henle in their family Lamnoidea, which is 

 stated to have the caudal fin in the form of a crescent, 

 with a lateral keel and a distinct dimple ; the second 

 dorsal and anal fins opposite. 



Pristiurus Bon. " Differs from Scyllium only by its 

 long snout, and by a series of larger scales, arranged 

 like a saw, on the upper edge of the tail." 



ChiloscyHium M. and H. * " Anal fin placed further back 

 than the second dorsal, and the last branchial opening 

 approximating to the fourth. The characteristic 

 mark of this genus is the broad membranaceous under 

 lip, separated from the skin of the throat by a kind 

 of furrow ; the upper nasal valve bears a cirrus. 

 (4 Sp.)" 



Loxodon M. and H. " Spiracles very small; teeth flat, 

 sharp, without serratures, as in Scohodon ; a dimple at 

 the root of the tail ; caudal fin as in Galeocerdo, but 

 the lower lobe has only one incision. (] Sp.)" 



Triglochis M. andH. '^ Spiracles small; branchial open- 

 ings large, as in Lamna ; tail as in Carcharias, but 

 without the dimple ; the first dorsal placed before the 

 ventral, and the second between the ventral and the 



• No examples of MM. Miiller and Henle's genera have been given, 

 which still further increases the difficulty of understanding them. 



f We have before expressed our opinion on the very artificial nature of 

 the arrangement of the cartilaginous fishes by Miiller and Henle, as ex- 

 hibited in their paper already quoted ; nevertheless, we deem it advisable to 

 insert most of their subdivisions, that they may be hereafter compared 

 with those of Rafinesque, and the priority of nomenclature to such as are 

 detained be equitably adjusted. 



