NERVOUS SYSTEM. VERTEBRATA. 



179 



The cerebellum conforms to the type presented by the 

 smaller Marsupials, but the folia are much more numerous. 

 In most other Orders of mammals we find in the larger 

 members that the cerebellum becomes more compact, and 

 the region behind the primary (preclival) fissure ceases to 

 assume the hood-like form covering the anterior lobe. As 

 a result of the slighter degree of expansion of this part of 

 the cerebellum in such mammals, the exposed medullary 

 area becomes greatly reduced, or even disappears. But in 

 the Kangaroo this does not happen. The type of the 



Fig. 57. (xf.) 



smaller members o the Order with a hood-like covering 

 for the anterior lobe and exposed medullary areas is re- 

 tained, as it is in the Thylacine ; and the only difference 

 consists in the larger size of the organ and a richer supply 

 of fissures, and consequently more numerous folia. 



0. C. 1323 A a. 

 Ziehen, Jena. Denkschr., Bd. vi. 1897, p. 54. 



D. 213. The left cerebral hemisphere, optic thalamus, and part of 

 the mid -brain of a Giant Kangaroo (Macropus giganteus). 



There is a typically prolonged calcarine Sulcus, and the 

 genual and rostral sulci are joined. 



There is a well-developed sulcus A the " Sylvian fissure" 

 of most writers. The sulcus B, the " suprasylvian " sulcus, 

 and the " coronal " sulcus are joined to form a large arc. 

 There is a large presylvian sulcus. 



N2 



