OCR Text |
Show 482 PROF. W. H. FLOWER ON THE [Nov. 11, afforded by characters of the cranium, digestive and reproductive organs*. f The Dogs (Cynoidea) are very uniform in their cerebral characters, having always four distinct and regular gyri surrounding the fissure of Sylvius, which is short and approaching a vertical direction. The first and second arched gyri have the anterior and posterior limbs equal, the third has the posterior limb broad and bifurcated. All the other Carnivora have only three arched gyri on the outer surface, the first, or lower one of the Dogs, being either wanting or concealed beneath the second, within the fissure of Sylvius f. In the Arctoidea the fissure of Sylvius is rather long and slopes backwards; the inferior gyrus has the limbs long, corresponding with the length of the Sylvian fissure; the anterior rather narrower than the posterior (especially in the true Bears) ; the middle gyrus is moderate and equal-limbed; the upper one large, very broad in front, and distinctly marked off from the second posteriorly as far as near the lower border of the temporal lobe J. The crucial fissure is long and oblique, and situated further back than usual. In the AHluroidea the Sylvian fissure is moderate and nearer to the vertical than in the last group. The gyrus which immediately surrounds it is wide, especially the posterior limb, which is generally twice the width of the anterior, and is divided by a vertical fissure, well marked in the Cats and Hyaenas. In the Cats the anterior limb is also partially divided. In the Civet both limbs are simple§. The second gyrus is moderate and simple. The superior gyrus is wide in front, but small posteriorly, the sulcus which separates it from the second not extending quite to the hinder apex of the hemisphere. MOUTH, TONGUE, ETC. The incisor teeth, both above and below, were worn down almost level with the gums; the ends of the canines were also truncated and broken. Behind the canines there were but three teeth above and two below on each side, all, as usual, quite small and rudimentary. The roof of the mouth is broad and nearly flat. It has four strongly marked, sharp-edged, curved ridges passing completely across from side to side, with tbe concavity of their curve turned backwards. The first is between the incisors and the canines ; the second is opposite to the latter. The middle of the fourth ridge is one * See " On the Value of the Characters derived from the Base of the Cranium in the Classification of the Carnivora" (P. Z. S. 1869, p. 4). t In the Hycena.its hinder limb is partly exposed. X Except in the smaller members of the genus Mustela, where the sulcus separating the superior from the middle gyrus is less produced posteriorly than in others of the group. In Galictis vittata, however, the brain is quite a miniature of that of a Bear; but the middle convolution is united with the upper one at its superior anterior angle. According to Leuret, a similar union is found in the Otters. § The Suricate agrees with the Hyienas rather than with the Civets in the general characters of its brain-convolutions. |