802 



ON THE BRAIN OF HYDBOCHffiRTTS. 



[June 20, 



The third fissure c, which runs parallel or approximately so to the 

 last, is also a perfectly constant fissure iu the Capybara's brain. 



The temporal lobe has further other slight fissures which are so 

 irregular that I think it hardly worth the trouble of describing 

 them. 



Fig. 4. 



Brain of Hydrochcerm, inner Tiew of hemispheres. 



Now we come to the fissure d of my former paper on the Eodent's 

 brain. In one of the three brains at my disposal it passes outward 

 and forward from the fissure a on both sides, or rather fi'om the 

 margin of the knee-shaped bridging convolution, already referred 

 to. If this region of the brain be compared with my figure of that 

 of Gulo, a striking likeness will be apparent, suggesting that the 

 fissure d is the crucial sulcus of the Carnivora. In the two other 

 brains the fissure was not so clearly marked. 



Sylvian Jlssure. — Dareste has remarked that this fissure appears 

 to be absent in the Capybara. It is certainly not at all plain in 

 any of the three brains which I have examined myself. But 

 nevertheless I do not think that it can be said to be totally un- 



rig. 5. 



Brain of Hydrochmrus, inner view. Nat, size. 

 A , calcarine (?) fissure ; B, 0, parieto-occipital ; E, calloso-marginal. 



represented. On viewing all these brains from the dorsal aspect, 

 a prominent and obliquely (or, in one case, transversely) running 

 fissure is to be seen which separates ofE the wider posterior region 

 of the hemispheres from the anterior narrower portion (fig. 1, s). 

 It coincides, in fact, in position and direction with what seems to be 

 undoubtedly the Sylvian fissure in Lagostomus (P. Z. S. 1892, p. 599, 



