i8o 



S. W. WILLISTON. 



probably, was inherited from the cotylosaurs, between the parietal, 

 paroccipital and squamosal, the posttemporal vacuity. By an 

 emargination of the roof from behind, the squamosal may become 

 separated from the parietal, and by an emargination from below, 



FIG. 12. Lycosuchus, after Broom. 



from the postorbital, indeed, entirely isolating it in the arch. In 

 such cases a large fossa is disclosed from above, which is some- 

 times, tJwitgJi incorrectly, called the supratemporal fossa. Baur 

 some years * ago called attention to the fact that the turtles have 

 no supratemporal fossa or fenestra. In fact, the temporal roof of 

 the turtles throughout seems to be quite like that of the cotylo- 

 saurs, judging from Seeley's description : 2 " While the temporal 

 vacuities are roofed over in Pareiasaurus, the roof is like the 

 primitive roof of the genus Chelone, whereas in Professor Cope's 

 figures of Empedias the skull appears to be closed behind as in 

 Gorgonopsia." That the turtles ever had a supratemporal fen- 

 estra is quite out of the question. How, then, is it possible to 

 derive them from the Anomodontia (sens. lat.\ or from any 

 known group of reptiles save the Cotylosauria ? The entire ab- 

 sence of the quadratojugal bone, or any ossification corresponding 

 to that bone in the Testudinata, in all the Anomodontia, Therio- 

 dontia, Placodontia and Therocephalia is exceedingly difficult to 

 explain, if they are ancestral to the turtles. Has this bone reap- 

 peared, after its loss or close fusion with other bones ? I am 

 aware that many attempts have been made to show the relation- 



1 Jour. Morph., iii., p. 472, 1889. 

 1 Phil. Trans., 1894, p. 1009. 



