26 



(»PE 



Fig. I.—Heptanchus griseus left pectoral fin, pluribasal type; SB, scapular arch; 

 JVL, foramen; Fr, propterygium; JKs, mesopterygium; a, 6, axis of metapterygium; 

 Sa, basilars; FS, aotinotricliia. From Wiedersheim. 



The families of the Asterospondyli differ as follows : 



I. Teeth molariform.* 



Teeth separate ; (1) Cestraciontidae. 



Teeth confluent ; (2) Cochliodontidse. 



II. Teeth with elevated cusps. 



(3) Hexanchidse (Fig. 7). 



(4) Sq/lliidse. 



(5) Lamnidse. 



(6) Carchariidse. 



The distribution of these families in time is as follows : 



* Except ^ome Cestraciontidae. 



