184 PHYSIOLOGICAL SERIES. 



the paucity of sulci. There is a short sulcus A (" Sylvian 

 fissure ") on the right side, but it is almost completely 

 aborted on the left side. There is a short deep paramcilian, 

 the characteristic Macropod, sulcns ; and also a small 

 prorean sulcus. No other sulci are found on the cranial 

 surface. But there are a number of shallow ill-defined 

 depressions which conform to no known pattern. 



On the mesial surface there is the characteristic, oblique, 

 prolonged calcarine sulcus and a more characteristic inter- 

 calary sulcus than is usually found in Marsupials. The 

 features of the cerebellum, and in fact of all parts of this 

 brain, are demonstrated with exceptional clearness. 



O.C. 1323 A^. 



Beddard, Proc. Zool. Soc. 1895, p. 136. 



Family PHASCOLOMYID^E. 



D. 222. The brain of a Wombat (Phascolomys ursinus), in which 

 the left hemisphere has been separated from the rest of the 

 brain. 



The short, broad, blunt anterior extremities of the hemi- 

 spheres of this brain form a marked contrast to the pointed 

 anterior poles of most other large Marsupials, such as the 

 Kangaroos and especially the Thylacine. 



The cerebral sulci are in many respects peculiar. Per- 

 haps the most significant feature is the absence of a well- 

 defined calcarine sulcus, which is such a constant feature 

 in the Marsupialia, and also in the Eutheria with the ex- 

 ception of the peculiar Order of Rodents. 



A typical orbital (presylvian) sulcus, such as we find in 

 the Carnivora, appears to spring from the rhinal fissure far 

 forward near the olfactory bulb. It is prolonged back- 

 ward under a small operculum, which meets the lower 

 (pyriform) lip of the rhinal fissure, and then appears to 

 curve upward again in what may be called the Sylvian 

 region (fig. 60, A). This apparent upturned caudal ex- 

 tremity of the orbital sulcus, which may be regarded as 

 the representative of the sulcus A of the Kangaroos, 

 presents a close resemblance to the arrangement found in 

 many Viverridse (e. g. the Civet, vide infra) . [A com- 

 with the latter will indicate why the two sulci A and 



