NERVOUS SYSTEM. VERTEBRATA. 221 



the cerebellar hemispheres, and especially of the olfactory 

 bulbs. 



Gervais, Nouv. Arch. Mus., t. v. 1869, p. 38. 



D. 278. The brain of a Hoffmann's Sloth (C/wloepus lioffmanni) . 



This brain closely resembles that of the ordinary Two- 

 toed Sloth. 



In this specimen the anterior extremity of the supra- 

 sylvian sulcus opens into the rhinal fissure, and a curious 

 triangular depression is found behind the junction. This 

 is more pronounced on the right hemisphere and presents 

 a curious resemblance to the fossa Sylvii. There is, how- 

 ever, no true Sylvian fissure, although on the left hemisphere 

 the pit-like representatives of the compensatory supra- 

 sylvian sulci open into the rhinal fissure so as to produce 

 a spurious resemblance to it. 



It is instructive to note in this specimen how in the 

 pyriform lobe the operation of factors such as produce the 

 pseudosylvian sulcus in the neopallium of many mammals 

 has converted the vallecula Sylvii into a sulcus like the 

 neopallial pseudosylvian sulcus of other forms. 



On the left hemisphere there are two coextensive sagittal 

 sulci, the mesial of which may represent either the 

 "lateral " or 6i entolateral " sulcus, and the external may 

 be either the caudally prolonged " coronal " or the " lateral " 

 (see account of specimen D. 276). 



On the right hemisphere the condition resembles that 

 of specimen D. 276. None of these cranial sulci join the 

 calcarine. 



There are well-developed post-lateral and paracalcarine 

 sulci. 



Turner, Journ. Anat. & Phys., vol. xxv. 1890, p. 122. 



Family MEGATHEEIID^E. 



^ 



D. 279. A cast of the cranial cavity of a Megatherium cuvieri. 



This presents an extraordinarily close resemblance to the 

 Bear's brain, but is considerably larger. 



There is a deep oblique depression in the '* Sylvian 

 region," and appearances suggest that there was a long 



