198 PHYSIOLOGICAL SERIES. 



the calcarine (splenial) sulcus. It extends upward so as to 

 slightly notch the dorso-caudal margin of the hemisphere. 



The corpora quadrigemina are partially exposed. 



According to Beddard other sulci may be present in il it- 

 pallium. 0. C. 1323 E c. 



Gervais, Journ. de Zool., t. i. 1872, pi. xxiii. fig. 7. 

 (In this memoir cranial casts of numerous Rodents 



are described.) 



Family HYSTRICIDJE. 



D. 246. The brain of a Porcupine (Hystrix sp.). 



The cerebral hemispheres are very broad. (Their 

 posterior extremities do not diverge in the manner Beddard 

 describes, and the corpora quadrigemina are quite hidden.) 



The base of the brain resembles in shape that of the 

 Beaver, but the rhinal fissures are deep and well-defined. 

 There are two chief sulci and several pit-like depressions on 

 the pallium. 



A short shallow posterior furrow runs parallel to the 

 interhemispheral cleft and resembles the para median 

 sulcus of the Kangaroos. 



There is a longer oblique sulcus further forward which 

 cannot be strictly compared to any sulcus in other 

 mammalian brains. It is impossible to say with any decree 

 of certainty whether it represents the supmsylvian or a 

 lateral element of such a form as the Capybara. 



There is no Sylvian fissure, although Beddard describe- 

 such a fissure in his specimens. 0. ( >. 1323 E e. 



Beddard, Proc. Zool. Soc. 1892, p. 600. 



D. 247. Th(5 brain of a Canadian Porcupine (Erithizon dorsatum}. 

 This brain i- much more like that of the Coypu than 

 the Porcupine. Its pallium is quite devoid of sulci. 



0. C. 1323 Km. 

 Presented by St. George Mivart, Esq. 



D. 248. The brain of a Mexican Tree- Porcupine (CwnoJon 

 mexicanus) . 



This brain resembles that of the Canadian Porcupine. 

 Its pallium is entirely free from sulci, but is grooved in all 

 directions by vascular furrows. 0. C. 1323 E k. 



