204 



THE LOWER PRIMATES 



extremity of the frontal lobe separating a small inferior frontal convolution 

 from a large superior frontal convolution. Several indefinite, interrupted sulci 

 are seen on the orbital surface of the frontal lobe. Upon the mesial surface 



FIG. III. DORSAL SURFACE OF BRAIN, MYCETES SENICULUS. 



[Actual Length, 46 mm.] 



Key to Diagram, fis. p. o. lat., Fissura Parietooccipitalis Lateralis; sulc. prec. inf., Sulcus Precentralis 



Inferior; sulc. retrocent. inf.. Sulcus Retro-centralis Inferior; sulc. temp, sup.. Sulcus Temporalis 



Superior. 



the indication ot the general line and direction of the marginal sulcus is 

 indicated by a scries of interrupted fissures. The calcarine and collateral 

 fissures are well defined, as is also the supracallosal fissure. The corpus 

 callosum is larger than in marmoset and lemur. The splenium in particular 

 is somewhat thicker than in the lower forms already considered. 



The lateral appearance of the hemisphere in myeetes gives the impres- 

 sion of a marked advance as compared with lemur and marmoset. The brain 

 is definitely gyrencephalic and its fissural patterns are rendered conspicuous 

 by the appearance of the well-marked Sylvian sulcus which is no longer 

 dominated by any suggestion of a circumsylvian arrangement of convolu- 

 tions. Although there is no such marked development in the sulcus simiarum 



