88 On the Generic Characters 



is odd enough, that I collected, (in the summer of 1820), from 



that locality, the best green sand fossils I have in my museum.''' 



(To be continued). 



Art. VII. On the generic characters of Cartilaginous Fishes, with 

 Descriptions of new genera. By Dr. J. Muller, Professor of 

 Anatomy and Physiology at the Royal University of Berlin ; and 

 Dr. Henle. Communicated by the Authors. 

 [Continued from page 37). 



The three following genera are all as different from each other 

 as from the preceding group ; and would, therefore, in a sys- 

 tem, take the place of families. 



TRIGLOCHIS, Nob. 



Large "branchial openings and small spiracles, as in Lamna. The tail 

 like Carcharias, but without the dimple. The first dorsal fin stands before 

 the abdominal ones; the second dorsal between the abdominal and anal fins; 

 they are all pretty large. Teeth long, pointed, with one lateral denticle, or 

 two on each side. We are not acquainted with the valve of the intestine. 



To this genus, or to a very confined one, will probably be- 

 long the genus Odontaspis, Agassiz ; the author himself refer- 

 ring to it the Squalus ferox, Risso, which has all the charac- 

 ters of our Triglochis. 



ALOPECIAS. 



Head, dorsal and anal fins, and spiracles, as in Lamna, (the latter having 

 been hitherto overlooked), but the branchial openings are small, and the 

 last above the pectoral fins, and the upper lobe of the caudal fin, extremely 

 elongated. A dimple on the tail, but no lateral keel. Teeth sharp, trian- 

 gular, without serrature or protuberance. Intestinal valve in a spiral. (1 sp.) 

 CESTRACION. 



Branchial openings as in Alopecias ; second dorsal fin between the anal 

 and abdominal ones, like Triglochis. Spiracles small. Teeth arranged in 

 pavement ; the anterior rows small and pointed. A prickle or sting before 

 each dorsal fin. (1 sp.) 



The Sharks of the third division possess, like the preced- 

 ing, an anal, but only one dorsal fin, and six or seven bran- 

 chial openings. It is the genus Notidanus, Cuv. which we 

 divide, with Rafinesque, into two genera ; Hexanchus, with 

 six branchial openings, (1 sp.) and Heptanchus, with seven. 

 (2 sp.) 



The fourth division of the Sharks, without an anal fin, we 

 separate into two groups ; the first of which has a sting be- 

 fore every dorsal fin; the second wants this sting. Both have 

 spiracles, and are without the membrana nictitans. 



The group with dorsal stings, {Acanthorhinus, Blainv.) con- 

 tains four genera : — 



1. Acanthiat, Bonap. Teeth with a transverse edge, the point being di- 

 rected outwardly, of the same shape in the upper and the lower jaw. — 

 (4 sp.) 



