118 THE VOYAGE OF H.M.S. CHALLENGER. 



and as the last named was partially divided by an antero-posterior fissure into two, it 

 looked as if it might represent both the sagittal and the mediolateral convolutions of the 

 Doo- and Walrus. On opening up the Sylvian fissure I found to my surprise that a 

 definite arched convolution was completely concealed within it. It was separated from 

 the convolution which bounded the Sylvian fissure by a deep fissure which was also 

 concealed. Its anterior limb, not quite so bulky as the posterior, was continued into 

 the supraorbital area immediately external to the rhinal fissure, and to the outer root of 

 the olfactory peduncle. Its posterior limb reached the postrhinal fissure and the lobus 

 hippocampi. I could not but think that we had here, more completely than either in 

 tbe Walrus or Seals, a sinking into the Sylvian fissure of the convolution which ought 

 to have bounded it, so that both the Sylvian convolution properly so called, and the 

 suprasylvian fissure, were concealed within it. If this be a proper explanation of the 

 arrangement, then the three convolutions on the cranial aspect would be sagittal, medio- 

 lateral, and suprasylvian ; whilst the two complete curved fissures between them would 

 be the mediolateral and lateral. The 1st curved fissure therefore into which the coronal 

 fissure is prolonged, would then as in the Dog be the mediolateral fissure. The olfactory 

 apparatus was large, and the external root formed a thick broad band of connection with 

 the lobus hippocampi, so that the Sylvian fossa was shallow. 



In the Badger (Meles taxus) the postrhinal fissure was deep and prolonged towards the 

 splenial fissure, from which it was separated by a short retrolimbic gyrus ; anteriorly the 

 splenial fissure was continuous with the crucial fissure ; a short prsecruciate fissure marked 

 off a small ursine lozenge, consisting of a single convolution, and situated about the 

 junction of the anterior and middle third of the dorsum of the hemisphere. The supra- 

 splenial was not differentiated from the sagittal convolution. The crucial fissure was 

 18 mm. long, and bounded by a relatively large sigmoid gyrus, the posterior limb of 

 which was continuous with the sagittal convolution. Below and behind the sigmoid 

 gyrus was the coronal fissure, which was continued backwards into the 1st curved 

 fissure, but not forwards into the prsesylvian fissure. Only three convolutions sur- 

 mounted the Sylvian fissure, the anterior limb of the Sylvian convolution was partly 

 concealed in that fissure, the suprasylvian and marginal convolutions were distinct, and 

 the latter was not divided into a sagittal and a mediolateral convolution. The olfactory 

 apparatus was large. 



In the Ratel (Mellivora indica) the postrhinal fissure was deep and separated from 

 the splenial fissure by a short and partially concealed retrolimbic gyrus. The callosal 

 convolution was relatively wide and closely resembled in its proportion the corresponding 

 convolution in the Otter as figured by Broca {pp. tit., fig. 1, p. 399). The splenial fissure 

 terminated a little in front of the middle of the dorsal surface of the hemisphere in 

 the crucial fissure ; a short prsecruciate fissure was also present, and between it and the 

 crucial fissure was a distinct ursine lozenge formed of a single convolution. The marginal 



