-100 PEOF. G. ELLIOT SMITH ON THE 



Meynert refused to re:?arcl it as the "crucial" sulcus, and called it "centi-al." In the 

 Viverridae it is often absent, and its simplest form is exhibited in some of the members 

 of this family as a small depression on the dorsal surface of the hemisphere, a short 

 distance in front of the outwardly-bent anterior end of the lateral sivlcus. 



The ansate sulcus is a branch of the lateral, which develops behind the crucial sulcus. 

 It is not constant, and when present is subject to great variation. 



Much less constant than any of these furrows is the sulcus wliicli Krueg calls 

 "diagonalis." It is often present in the Felida- as a separate element: more often its 

 identity is lost by merging into tlie anterior ectosylviau sulcus or the suprasylvian. 



Tf we represent graphically the inferences draAvn from the foregoing discussion as to the 

 features of the primitive Carnivore, a scheme such as the accomiianying diagram (fig. 57) 

 would be the result. This is practically the brain of Vicerra. 



Fig. 57. 

 scr. ^f'- si. 



SCO. 



ss. 



Jr. ."ps. 



A selicmc representing the sulci in a liypotheticnl generalized Carnivore. 



That this is really the primitive Carnivore type will be shown by an examination of 

 the brain-casts of the Eocene Carnivora. 



Thus in a natural cast of the brain of Sfenoplesiclis Co//l/ari in the British Museum 

 (M. 1723) there is a conjoint corono-lateral sulcus (which is quite sagittal in direction) 

 and a well-defined suprasylvian sulcus, as in Viceira. There is r;o sign of crucial, 

 ])seudosyIvian, or postsylvian sulci. 



Fig. 58. 



Steiinplesicl.is Cai/lii.ri. Dorsal aspect of a natural cast of the cranial cavity. Xat. size. 



In the excellent natural cast of the cranial cavity of CijHoliijcBnodoii Cayluxi (British 

 Museum, M. 4199)— another Carnivore, which, like aSV^»o/j/(^'s/c//.s\ comes from the Upper 

 Eocene formations of France — w^e find similar lateral and suprasylvian sulci, and two verv 

 shallow furrows representing the pseudosylvian sulci [a similar phenomenon is often 



