CEREBRAL COKVOLUTIONS OF THE CARNIVORA. 21 



They also almost all differ from the Cynoidea by having generally 

 a junction between the hippocampal and sagittal gyri, and, almost 

 uniYersally, by the possession of a precrucial " Ursine lozenge." 

 They also differ from the ^luroidea in that they have the 

 "Ursine lozenge"; in that the anterior limb of the Sylvian 

 gyrus tends to be, and very often is, much more slender than its 

 posterior limb. They also differ from all non-feline ^Eluroids by 

 mostly hariug a junction of the hijDpocarapal and sagittal gyri 

 behind the crucial sulcus. The Arctoids also differ from all 

 other Carnivora by their tendency to a greater development in 

 breadth and complexity of the sagittal gyrus. 



The Pinnipedia. 



The cerebrum of the Seals *, as is well known, is very dif- 

 ferent in aspect from any of the brains of the true Carnivora 

 whether the latter are purely terrestrial or more or less aquatic 

 in their habits. It is generally more rounded in form and more 

 richly convoluted, while the circum-Sylvian gyri are less distinct 

 and easily defined, the parietal and sagittal sulci especially blend- 

 ing ; moreover the crucial sulcus does not appear, when the brain 

 is placed beside that of the true Carnivora. 



Cystoplwra. — The brain of this genus is well represented in the 

 collection of the Eoyal College of Surgeons. It shows a Sylvian 

 fissure of moderate extent and somewhat vertical in position. 

 The Sylvian gyrus is very complex and contorted, and joins the 

 parietal gyrus by bridging convolutions, which are not constant 

 in position. The latter gyrus ends abruptly a considerable 

 distance behind the anterior end of the sagittal gyrus, which 

 attains the front edge of the cerebral hemisphere and, as usual 

 surrounds the crucial sulcus. This latter sulcus is invisible or 

 all but invisible, when the dorsum of the cerebrum is looked at 

 owing to its being placed much further forwards than in any of 

 the true Carnivora, namely quite at the anterior end of the 

 cerebrum. 



Phoca'f. — In the brain of a Common Seal, which I had 

 extracted for this paper, I found some very interesting con- 

 ditions. Grenerally, the convolutions were like those of the form 

 last noticed, and though a crucial sulcus could be detected at 



* See Leuret, I. c. p. .390, pi. xi. ; and Krueg, p. 642, and pi. xxxviii. 

 f See Leuret, p. 390, pi. xi. 



