REPORT ON THE SEALS. 117 



volution which represents this area was not definitely defined. Dr. Mivart attaches 

 much importance to the presence of the ursine lozenge in the Pinnipedia, as indicating 

 phylogenetic relations to the ursine group of the Carnivora. 



I shall now compare the convolutions on the mesial and tentorial surfaces of the 

 hemisphere in the Pinnipedia with the corresponding surfaces in the brains of several of 

 the Canidse, and the brains which I have examined are those of the Dog, Jackal, and Fox. 

 In all these animals the postrhinal fissure joined the splenial fissure as in Phoca vitulina. 

 The splenial fissure on the tentorial surface was not bridged superficially by a retro- 

 limbic convolution. The lobus and the hippocampal and callosal divisions of the gyrus 

 fornicatus were definitely expressed. The splenial fissure was continued at its anterior 

 end into the crucial fissure, which was placed in the anterior third of the dorsum of the 

 hemisphere. In none of these brains was a suprasplenial convolution differentiated from 

 the sagittal convolution by a suprasplenial fissure, though in the Dog's brain an indica- 

 tion of such a fissure was present. The crucial fissure was bounded by the sigmoid 

 gyrus, which was continuous with the sagittal convolution. Immediately external to the 

 sigmoid gyrus was the coronal fissure, which was continued backwards into the medio- 

 lateral fissure, but not forwards into the prsesylvian fissure. There was neither prse- 

 cruciate fissure nor ursine lozenge. The olfactory peduncle was both relatively and 

 absolutely larger than in the Seals and Walrus notwithstanding the much smaller brain, 

 and the continuity of its large root with the lobus hippocampi was plainly marked across 

 the fissure of Sylvius. 



In the Polar Bear (Ursus maritimus) the postrhinal fissure was deep, and passed 

 back towards the splenial fissure, but was separated from it by a slender retrolimbic 

 gyrus partially sunk in the fissure. The anterior end of the splenial fissure was not con- 

 tinuous with the crucial fissure, but bifurcated ; the posterior branch reached the dorsum 

 of the hemisphere as a sulcus in the ursine lozenge, the anterior passed horizontally 

 forwards in front of the knee-like bend of the callosal convolution. The suprasplenial was 

 not differentiated from the sagittal convolution by a suprasplenial fissure, although there 

 was an indication of such a fissure posteriorly. The tentorial surface possessed both a 

 postsplenial fissure and a splenial convolution. The ursine lozenge was large, being 

 34 mm. long by 42 mm. wide. It formed a large proportion of the anterior third of the 

 dorsum of the hemispheres, and was partially intersected by small sulci, one of which 

 was the posterior branch of bifurcation of the splenial fissure. The crucial fissure was 

 40 mm. long. The sigmoid gyrus which enclosed it was strongly developed, and. its 

 posterior bmb was continuous with the sagittal convolution. The coronal fissure was 

 behind and to the outer side of the posterior limb of the sigmoid gyrus, and was 

 prolonged backwards into the 1st curved fissure, but not forwards into the prsesylvian 

 fissure. The Polar Bear had three distinct convolutions above the Sylvian fissure. It 

 seemed at first as if they represented the Sylvian, suprasylvian, and marginal convolutions, 



