34 



THE LOWER PRIMATES 



prominence of the lateral cerebellar lobes. In other words, the vermis 

 cerebelli is equally as conspicuous as the lateral lobes. 



In the tentorial surface, the folial sulci extend without interruption from 



'^%.'> 



FIG. 16. DORSAL SURFACE OF BRAIN, LEMUR MONGOZ. 



[Actual length, 43 mm.] 



Key to Diagram, c. Sulcus Centralis; i-is. silvii. Fissure of Sylvius; sllc. temp, sup., Sulcus 



Temporalis Superior. 



the vermis to the lateral lobes. On the occipital surface, however, two lateral 

 paramedian sulci interrupt the course of the interfolial grooves, as they 

 pass from the vermis to the lateral lobes. 



THE BRAIN STEM 



The markings on the several surfaces of the brain stem are not so 

 decisive as in many other species of primates (Fig. 20). 



The Oblongata. The oblongata upon its ventral surface presents a 

 ventromedian sulcus and two ventrolateral sulci. In the more cephalic por- 

 tion of the ventral surface the ventromedian sulcus is flanked on either side 

 by the pyramids which, in turn, are separated from the inferior olivary 

 eminences by the ventrolateral sulci. The pyramids become progressively 

 less well marked as they approach their caudal extremity, at which point 



