CALLITHRIX JACCHUS, THE MARMOSET 



i6i 



larl}' in the region of the postsplenial fossa. This concavity accommodates 

 the upward protrusion of the cerebelhim. The cerebeHum upon its tentorial 

 surface is almost completely overhung by the occipital pole of the hemisphere. 



FIG. 76. RIGHT LATERALSURFACE OF BRAIN, CALLITHRIX JACCHUS (mARMOSET). 



[Actual Length, 31 mm.] 

 Key to Diagram, ob., Oblongata. 



The superior vermal portion of the cerebellum is more conspicuous than the 

 lateral lobes which show but slight expansion. On the occipital surface the 

 vermis is also the outstanding feature. It represents scarcely less than a 

 third of this surface and stands out conspicuously against the poorly devel- 

 oped lateral expansions of the cerebellum. The two paramedian sulci 

 interrupt the passage of the interfolial fissures from the inferior vermis to the 

 lateral lobe. No such sulcus, however, exists on the tentorial surface. While 

 the cerebral hemispheres of marmoset assign the animal to a definite place 

 among the primates, the simplicity of the brain indicates the relatively low 

 position of the Hapalidae (Fig. 76). 



THE SURFACE MARKINGS OF THE BRAIN STEM 



The surface markings of the brain stem are in general much less dis- 

 tinct than m the higher primates. In many respects, they are less impressive 

 than in Lemur mongoz. The oblongata on its ventral surface presents a 

 ventromesial sulcus and two faintiv marked ventrolateral sulci. Neither the 



