of Cartilaginous Fishes. 89 



2. Spinax, Bonap. Teeth of the lower jaw as in the preceding; teeth of 

 the upper jaw with a long point in the middle, and two shorter ones on 

 each side. (1 sp.) 



3. Centrina, Cuv. Teeth of the lower jaw nearly straight, leaflike, with 

 a serrated edge, and a flat triangular point ; those of the upper jaw al- 

 so straight, hut more narrow, conic, pointed, forming a cluster in the 

 central part of the maxilla. (1 sp.) 



4. Centrophorus, Noh. The lower teeth have a transverse edge, indis- 

 tinctly serrated, the point of each being directed towards the corner of 

 the mouth ; the point of the upper teeth is directed downwards ; they 

 are equilateral, without any serrature. (1 sp. Sq. squamosus, Bl. Schn.) 



To a new genus, but which, perhaps, is nearly allied to this, 

 probably belongs the Squalus squamosus, Bl. Schn. with the 

 teeth of which we are not acquainted. 



The group without dorsal stings, (Scymnus, Cuv.) embra- 

 ces three genera : — 



1. Scymnus, Noh. Teeth in the upper jaw straight and narrow, in the 

 lower jaw crooked, pyramidal, equilateral. The first dorsal fin before, 

 the second behind, the abdominal fins. (2 sp.) 



2. Laemargus, Nob. The situation of the fins is the same as in the pre- 

 ceding, but the lower teeth have a transverse edge, as in Acanthias ; 

 the upper teeth are narrow, conic, straight, or curved outwardly. (3 sp.) 



3. Echinarrhinus, Blainv. (Gonoidus, Agass.) The first dorsal fin op- 

 posite to the abdominal ones. Teeth in both jaws broad and low, the 

 edge nearly horizontal. The lateral edges have one or two transverse 

 denticles. (1 sp.) 



The fifth and last division consists only of the genus Squa- 

 tina, (2 sp.) without an anal fin, with a protractile mouth at 

 the top of the head, and the peculiar and sufficiently known 

 form of the pectoral fins. 



Amongst the Skates, the genus Pristis should be placed 

 next to the Sharks, from the general shape of the body. The 

 Pristis cirrhatus, Lath, forms the type of our new genus, 

 Pristioph or us. 



The branchial apertures on the sides of the neck, before the pectoral fins, 

 which begin with a slender base, as in the Sharks ; the fifth branchial open- 

 ing approximates to the fourth, as in many Scyllia. Teeth pointed. (1 sp.) 



In Pristis, s. s. the teeth are pavement-like, and the branchial apertures 

 open on the inferior surface, as in the other Skates. (5 sp.) 



The family RHINOBATIS we form into two divisions 

 and five genera. 



a. First dorsal fin opposite to the abdominal ones ; caudal fin terminating 



in two lobes. Mouth undulated. 



1. Rhina, Schn. The nasal valve extending to the interior corner of the 



nostril. Body orbicular. Teeth round. (1 sp. 



2. Rhynchobatus, Nob. The nasal valve does not extend to the interi- 



or corner of the nostril. Body oval, as in Rhinobatus. The teeth 

 broader than long, elliptical. (1 sp.) 



b. The two dorsal fins placed upon the tail. Extremity of the caudal fin 



cut obliquely, forming only one lobe. 

 1 . Rhinobatus. The nasal valve like Rhynchobatus. (1 sp.) 



H 2 



