NOTES ON THE CANID.E OF THE WHITE RIVER OLIGOCENE. 375 



lateral sulcus. The suprasylvian sulcus is likewise very short and but little curved, and 

 is not divisible into anterior and posterior portions. The sylvian fissure itself is but 

 feebly marked upon the cast, but the rhinal sulcus, on the contrary, is very distinctly 

 shown and extends for nearly the whole length of the hemisphere. Making all due 

 allowance for the fact that a cast of the brain-case can but imperfectly reproduce the 

 features of the brain itself, yet it is clear that the cerebrum of Cynodictis was convolu- 

 ted in a much simpler way than in any of the existing Canidce, and that it retains char- 

 acteristics which among the modern dogs are embryonic and transitory. 



The cerebellum is rather large and is less overlapped by the hemispheres than is the 

 case among the recent members of the family. The vermis is narrow, but prominent, 

 and is quite clearly divisible into three lobes, corresponding apparently to the lobus cen- 

 tralis, lobus monticuli and declivus of Cards. The vermis is less regularly curved in the 

 antero-posterior direction than in the modern genus, the posterior surface forming nearly 

 a right angle with the dorsal. The lateral lobes of the cerebellum have quite a different 

 appearance from those of the recent Canidce. Thus, the lobus quadrangularis is less 

 extended transversely and narrows less toward the external side, while the lobus lunatus 

 inferior is very imperfectly developed, and the lobi semilunares appear not to be repre- 

 sented at all, or, if present, they must be exceedingly small. This latter point is difficult 

 to decide definitely, because a small fragment of the skull, which cannot be removed with- 

 out danger to the specimen, covers the place where the semilunar would be if present. 

 A small additional lobe, not represented in Canis, lies upon the dorsal surface of the 

 lobus quadratus and near to the vermis. Complex as it looks, the cerebellum of Cyno- 

 dictis is simpler than in the recent dogs. 



Jleasurements. 



No. 10513. 



Brain, length fr. cerebellum to olfactory lobe (incl.) 0.045 



Olfactory lobe, fore and aft diameter 005 



" " vertical diameter Oil 



Cerebrum, length in median line 030 



height at temporo-sphenoidal lobe .025 



width " " " " 030 



Cerebellum, length in median line 013 



" width 024 



vertical height 01S 



Medulla oblongata, width 012 



IV. The Vertebral Column. 



The backbone is not preserved entire in any of the specimens, but by the aid of 

 the more complete individuals from the John Day, the numbers of the various categories 

 of vertebra? may be inferred. 



a. p. s. — vol. xix. 2 v. 



