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Show 1892.] CEREBRAL HEMISPHERES OF RODENTS. 611 these furrows are, however, deeper than in Dasyprocta. The chief point of agreement between them, and that which causes them to differ from the two remaining families, is the absence of the Sylvian fissure; this brings Hydrochcerus into relation rather with the Dasyproctidae than the Caviidae, where it is placed by Alston. Judgingalso from Dareste's figure, the general outline of the brain of Hydrochcerus is like that of Ccelogenys, but also of Lagostomus. In all these three genera the principal longitudinal fissure, which I have called " a," is divided into two portions, one anterior and one posterior. Apart Brain of Aulacodus, viewed from above. Sy, Sylvian fissure ; a, longitudinal furrow. from this the brain of Lagostomus appears to be nearer to that of Dolichotis. They have both of them a deep Sylvian fissure, and the furrows b and c tend to converge towards the middle line; finally, the rhinal fissure in both genera is deeper behind than in front. I have not ventured to treat at length of the evidences of affinity afforded by the convolutions, since the illustrations are before the reader, who can form his own opinions. List of Papers and Books referred to. (1) D A R E S T E , C . - " Note sur le Cerveau des Rongeurs et particu-lierement sur le Cerveau du Cabiai," Ann. Sci. Nat. ser. 4, vol. iii. (1855), p. 355, pi. xi. (2) T U R N E R , Sir W . - " T h e Convolutions of the Brain: A Study in Comparative Anatomy," J. Anat. Phys. vol. xxv. pp. 105 -153 (1891). (3) B E D D A R D , F. E . - " Notes on the Anatomy of Dolichotis patagonica," P. Z. S. 1891, p. 236. (4) B E D D A R D , F. E . - " On the Brain and Muscular Anatomy of Aulacodus," P. Z. S. 1892, p. 520. (5) M I V A R T , ST. G E O R G E . - " N o t e s on the Anatomv of Erithizon dorsatus," P. Z. S. 1882, p. 271. |
