CEEEBEAL COlSTVOLTITIOlSrS OF THE CAENIVOEA, 



19 



tional manoer, and forming, on eacli side, tlie boundary of the 

 median longitudinal fissure of the cerehrum. 



JJrsus. — The Bear's brain has been carefally described and ad- 

 mirably figured by MM. Leuret and G-ratiolet *. I have examined 

 the brains of nearly all the species, including that of the Sloth- 

 Bear {Melursus). In all, the Sylvian sulcus has its anterior limb 

 very much narrower than its posterior limb ; in all, the parietal 

 gyrus is simple and single ; in all, the sagittal gyrus is very 

 complex, and tends to become longitudinally divided into two ; 

 it is greatly expanded and much convoluted anteriorly. In all the 



Dorsal surface of brain of TJrsus maritimus, talf natiu'al size. 



C. Crucial sulcus. P. Parietal gyrus, jpc. Precrueial sulcus. *S'. Sylvian 



gyrus. Sa. Sagittal gyrus. Sf. Sylvian fissure. 



species, the Sylvian fissure is exceedingly long and very oblique ; 

 and in aU. the hippocampal gyrus joins the sagittal gyrus, a 

 bridging convolution dividing the crucial and calloso-marginal 

 sulci. Finally, in the Bears we find present a large and very 

 marked " Ursine lozenge," which in them attains its maximum of 

 distinctness. It may be formed in different ways, either by 

 secondary sulci proceeding forwards from the crucial sulcus, or 

 by such sulci independently placed in front of it ; and the con- 

 dition may vary on the two sides of the same brain. 



* See I. c. p. 375, pi. vi. ; and P. Gervais, I. c. p. 134, pi. viii. fig. 10 (cast), 

 and pi. ix. fig. 9 (brain itself) ; also Krueg, /. c. p. 635 and pi. xxxvii. ; and 

 Burt Wilder, I. c. fig. 10. 



2* 



