354 SKLAcnOlDKI. 



(iroup C. 2\eth small, either with a central cmp and one or two 

 small lateral citqx^, or ubtnse, the ci/s^« being ohsolcte. 



C. Musteliiia. 



1. A pit at the root of the tail ; a small pit behind the angle of the mouth. 

 Spiracles noue B. Tricrnodon, p. 383. 



2. No pit at the root of the tail ; labial folds well developed. 



Spiracles none ; teeth with acute cusps . . 9. Lepfocarcharras, p. 38-1. 

 Spiracles small ; teeth with acute cusps. . 10. 2'm/m, p. 3H4. 

 Spiracles small j teeth obtuse 11. Mustelus, p. 385. 



Fam. 2. LAMNID^. 



No nictitating membrane. An anal fin ; two dorsals, the first 

 opposite to the space between pectorals and ventrals. Nostrils 

 not confluent with the mouth, which is inferior. Spiracles none, 

 or minute. 



Group A. Teeth large or of moderate size. On each side of the 

 upper jaw, at some distance from the symphysis, there is one or 

 two teeth conspicuously smcdler than the others. 



A. Lamnina. 



1. Gill-openings veiy wide ; side of the tail tvith a keel. 



Teeth lanceolate, not sen-ated 12. Lainna, p. 389. 



Teeth triangular, serrated 13. Carcharodon, p. 391. 



2. Gill-openinf/s of moderate width ; .n'de of the tail without keel. 



Teeth lai'ge, awl-shaped, with small additional basal cusps. 



14. Odontaspis, p. 392. 

 Teeth of moderate size, triangular, not serrated. 



15. Alopecias, p. 393. 



Ghroup B. Teeth very small, numerous, conical, simple. GUI-openings 



very ivide . , B. Selachina. 



Side of the tail with a keel 16. Selache, p. 394. 



[^Teeth very small, tricuspid. Gill-openings rather narroiv. 

 First dorsal very low and long 17. Pseudotriacis, p. 395.] 



Fam. 3. RHINODONTID^.. 



No nictitating membrane. An anal fin; two dorsals, the 

 first nearly opposite to the ventrals. Mouth terminal. 



Side of the tail with a keel 18. Iihinodo7i, p. 896. 



