18 MR. ST. GEOEGE MITAET OK THE 



condition of brain-surface which characterizes the smaller forms 

 of each group of Mammals. Nevertheless, tlie three circum- 

 Sylvian gyri are all distinctly present, though, as has been re- 

 marked by Professor Flower *, the sulcus separating the sagittal 

 and parietal gyri is less produced posteriorly in them than it is 

 in other species of Carnivora. They have, however, a long and 

 oblique Sylvian fissure. The Sylvian gyrus seems generally to 

 have its posterior limb the narrower. The parietal sulcus does 

 not communicate with the sagittal, save at the ends of the, 

 posteriorly short, sulcus which divides them. The sagittal gyrus 

 is much the widest of the three circum-Sylvian gyri. There is a 

 considerable crucial sulcus which is placed rather far back. In 

 front of it there is either an unmistakable " Ursine lozenge," or 

 a distinct trace of it. The crucial and calloso-marginal sulci 

 unite. 



Ictonyx. — The brain of the Zorilla h as been well figured by 

 Professor P. Gervais f. Its Sylvian fissure is long and oblique. 

 The Sylvian gyrus is much narrower in front than it is behind 

 the Sylvian fissure. The parietal gyrus is simple. The sagittal 

 gyrus is wide, especially towards its anterior end. The crucial 

 sulcus is large, and placed rather far back, a considerable, or 

 moderate, part of the cerebrum lying in front of it. There is 

 a distinct, but small, "Ursine lozenge;" and the hippocampal 

 gyrus is divided from the sagittal by the junction of the calloso- 

 marginal and crucial sulci. The sulcus which divides the parietal 

 and sagittal gyri does not extend far backwards in this genus any 

 more than in Mustela, ceasing near the posterior superior angle 

 of the cerebrum. 



Selictis. — The brain of this animal has been described and 

 figured by the late Professor Garrod J. The anterior limb of 

 the Sylvian gyrus is much the narrower ; the parietal and sagittal 

 gyri unite at the posterior superior angle of the cerebrum, as 

 in Ictonyx. The calloso-marginal and crucial sulci unite and 

 separate the hippocampal and sagittal gyri. There is a very 

 distinct " Ursine lozenge," but it is open behind owing to the 

 non-junction medially of the two halves of the crucial sulcus, 

 each hippocampal gyrus rising to the surface in a most excep- 



* P. Z. S. 1869, p. 482, note %. 



t See I. c. pi. ix. fig. 4 ; for a notice, see p. 144. 



\ See Proc. Zool. Soc. 1879, p. 307, figs. 1 & 2. 



