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Show 1895.] ME. F. E. BEDDAED ON THE BEAIX OF GULO. 141 Arctoidea, the anterior limb of the Sylvian gyrus is the longer. This is particularly marked above and leads toward the condition characteristic of Meles and Nasua, where the anterior limb of the Sylvian gyrus has the appearance of being tucked away iu its upper part below the surface of the brain. The parietal gyrus is connected by a bridging convolution with the sagittal gyrus. This is perfectly symmetrical on each side of the body and lies anteriorly on a level with the upper extremity of the Sylvian gyrus. At its extreme anterior end this gyrus becomes continuous with the Sylvian gyrus and, on one side, with the sagittal gyrus again. The sagittal gyrus, as is the rule with the Arctoidea, is wide and complicated. That part of the gyrus which is at right angles with the rest, and reaches the margin of the pallium, is divided by a longitudinal furrow, of which there are only traces in Galictis and Nasua and no traces in Meles. Brain of G-ulo (side view). Sy, Sylvian fissure ; c, crucial sulcus. ' I now come to the crucial sulcus (c), which is so important iu the Carnivorous brain and especially in the Arctoid. As in all Arctoidea, which are thus differentiated from the Ailuroidea, the crucial sulcus is situated comparatively far back. In Gulo the proportions of the lengths of the precrucial and postcrucial regions are 28 : 40. In Meles and Taxus they are more nearly equal, being 26 : 30. On the other hand, in Galictis they are 14 : 34. In Gulo, as in Galictis, the crucial sulci are nearly at right angles to the longitudinal axis of the brain. They do not reach the middle line, because in this region the hippo-campal gyrus emerges from below on to the upper surface of the brain, and becomes continuous anteriorly with the sagittal gyrus. The margins of this eruptive portion of the hippocampal gyrus form with the crucial fissure a Y-shaped furrow on each side, the lines of the Y being widely divergent and forming with each other a very obtuse angle. The median portion thus enclosed has been |
