NERVOUS SYSTEM. VERTEBRATA. 373 



D. 536. The brain of a Ring-tailed Lemur (Lemur catta), in 

 which the left hemisphere has been separated from the rest 

 of the brain. 



The deficiency of the lower end of the Sylvian fissure is 

 clearly shown. 



The composite character of the Sylvian fissure is well- 

 demonstrated in the left hemisphere of this specimen. The 

 lower extremity of the suprasylvian sulcus emerges from 

 the Sylvian complex. 



The peculiar hook-like appendage of the upper extremity 

 of the Sylvian fissure is also another reminder of the rela- 

 tionship of the suprasylvian (Sylvian) sulcus to the post- 

 sylvian (parallel), such as we have also seen elsewhere 

 in Myrmecophaga (Edentata). 0. C. 1337 A d. 



D. 537. The brain of a young Ring-tailed Lemur (Lemur catta). 

 The left cerebral hemisphere has been separated. 



In this specimen there is no trace of a separate supra- 

 sylvian element in the Sylvian fissure such as the last 

 specimen exhibited. The Sylvian is a straight, unbroken 

 fissure passing below into a deep cleft-like vallecula Sylvii 

 such as is found in the Apes. The upper extremity of the 

 Sylvian fissure is not hook-like, but the short sulcus (which 

 in the last specimen gave rise to the hook) is seen here in 

 the interval between the upper ends of the parallel and 

 Sylvian elements. 0. C. 1337 A a. 



Presented l>y J. Wiblin, Esq. 



D. 538. The brain of a Mongoose-Lemur (Lemur mongoz). 



Bristles have been inserted in the several cranial nerves. 



In this brain a small sulcus, such as that tentatively called 



" fronto-orbital," is present. 0. C. 9. 



Hunterian. 



D. 539. The brain of a White-faced Lemur (Lemur albifrons), 

 with its left cerebral hemisphere separate. 



The parallel sulcus of the left hemisphere of this brain is 

 interesting in comparison with those of the Ring-tailed 

 Lemur, for its upper extremity is hooked forward, t. e. 



