204 PHYSIOLOGICAL SERIES. 



On the left hemisphere of this brain the peculiar 

 characters of the rhinal fissure are very pronounced. The 

 anterior part of the anterior rhinal fissure is so faintly 

 marked, that the deep posterior part appears to be a back- 

 ward extension of the orbital sulcus. It is separated 

 by a wide interval from the posterior rhinal fissure. 



Note the peculiar lozenge-shape of the brain. This i- 

 well shown in a figure of Retzius's (Biolog. Untersuch., 

 Bd. viii. 1898, Taf. xii. fig. 1). 0. C. 1323 Ga. 



D. 256. A cast of the cranial cavity of a Capybara (Hydro- 

 clioerus capybara). [In duplicate.] 



This shows the true shape and proportions of the large 

 projecting olfactory bulbs : and the peculiar lozenge- 

 >hape of the brain as a whole, each cerebral hemisphere 

 having a most pronounced lateral angle slightly behind a 

 point midway between the anterior and posterior poles. 



Note also the exceedingly small relative size of the 

 cerebellum. 



Gervais, Journ. de Zool., t. i. 1872, p. 456. 



D. 257. The brain of a Patagonian Cavy (Doliclwtis magellanicn ) 

 ( $ ), from which the left cerebral hemisphere has been 

 separated (figs. 74 & 75). 



This brain is not so strikingly aberrant as that of the 

 Capybara. And yet the practical absence of well-defined 

 sulci on the mesial surface shows that this peculiarity of 

 the other Rodentia also occurs in this genus. There is 

 however a faint trace of a genual sulcus and a shallow 

 depression where one would expect to find the calcarine 

 sulcus. 



Unlike that of the Capybara, the brain of this Cavy 

 pi-e.-rni-. a typical well-defined rhinal fissure, such a> i- 

 seen elsewhere in the Rodentia, in the Rabbit for instance. 



There is an extensive sagittal sulcus parallel to and 

 coextensive with almost the whole length of the inter- 

 hemispheral cleft. This corresponds to the corono- lateral 

 -nlrtis of the Carnivora and Ungulata, and possibly also 

 to the prorean suleu- I'ux-d to the coronary element. 



A great vertical snlcus (s) pursues a slightly arched cnnr-c 

 upward from the junction of the anterior and po.-ierior 



