Chap. XVI.] 



SOME OTHER MAMMALS. 



269 



the Beaver. The Corpora Striata are said, by Stannius, 

 to be large in Bats, in many Rodents, and also in the 

 Edentata. 



Contiguous and posterior to each Corpus Striatum is 

 another rounded eminence, sometimes called the ' Optic 

 Thalamus,' but which it will be far better simply to 

 term the Thalamus. These bodies have previously been 



Fio. 86.— The Brain of the Dolphin, with the upper part of the Hemispheres cut off 

 —above the level of the Ventricle on the left, and so as to show this cavity on the 

 right side. (Owen, after Tiedemann.) b, Corpus callosum ; c, c, bottom of surface 

 fissures or 'sulci;' d, k, Corpus Striatum; h. Hippocampus, with its unusually 

 bioad free border or ' toenia ' (i) continued into the Fornix ; g, Thalamus. 



referred to in Reptiles and Birds, where they first show 

 themselves as projections developing from the upper and 

 inner aspects of the Cerebral Peduncles : in Quadrupeds, 

 however, owing to the backward extension of the Cerebral 

 Hemispheres, they seem to become included within these 

 and to project into the inner part of the floor of each 

 Lateral Ventricle. But in reality they lie outside these 

 parts. They are overlapped by the ' velum interpositum,' 

 a membrane constituting the roof of the Third Ventricle. 



