70 THE MAMMALIA OF THE DEEP RIVER BEDS. 



teriorly, the brain of the fennee {Cants zerda) has a very similar outline to that of 

 the fossil. 



We can best examine the sulci of the hemispheres after quoting Krueg's 

 description of the fissures which are characteristic of the recent Canidce : " Fissura 

 anterior und postica sind immer vorhanden, fast immer verbunden. Fissura coronalis, 

 ansata, lateralis, medilateralis meistens verbunden, letztere sowie die ectolateralis 

 immer vorhanden. Die Fissura splenialis ist haufig mit der rhinalis posterior, nur 

 ausnahmsweise nicht mit der cruciata verbunden. Die Fissura prorea, prascruciata, 

 postcruciata und confinis fehlen haufig und sind auch bei den grosseren Species nie 

 stark entwickelt" (No. 21, p. 614). In Cynodesmus the cerebral convolutions are 

 much simpler than in any existing species of Canidoe, even the smallest. Besides the 

 sylvian fissure, the dorsal aspect of the hemispheres displays but two slightly curved 

 sulci, one of which, the superior, is clearly the lateral sulcus ; its anterior portion 

 may, perhaps, represent the ansate and coronal fissures, but if so, all three are in the 

 same straight line. In the recent species the three are usually connected, but with 

 the difference that the ansate and coronal sulci are curved downwards and forwards, 

 out of the line taken by the lateral. The second fissure in the specimen is the supra- 

 sylvian, which is remarkably short and little curved, and is not continued into the 

 posterior suprasjlvian, which appears to be absent. The crucial fissure is not indi- 

 cated on the east, but no great stress can be laid upon this fact, for this sulcus is 

 sometimes not shown in the intracranial casts of recent species, the brains of which 

 actually possess it. If present, however, in Cynodesmus, it must have been extremely 

 short, as is shown by the straight course of the lateral sulcus and its nearness to the 

 dividing fissure between the two hemispheres. Among several brain casts of Miocene 

 carnivores, I have seen none which displays the crucial sulcus, though we can scarcely 

 believe that this fissure, which is now so characteristic of the recent families of the 

 order, had not then been developed. 



One very striking difference between the cerebral sulci of Cynodesmus and those 

 of the existing dogs, is the absence in the former of the posterior prolongation and 

 downward curvature of the fissures. The medilateral is lacking, and a minute, 

 isolated depression is all that can represent the ectolateral. Nor do I find any trace 

 of the presylvian (supraoi'bital) sulcus, or of the " fissura anterior und postica," 

 which, in the recent species, are always present and nearly always connected to form 

 a strongly curved sulcus between the sylvian and the suprasylvian. It is of interest 

 to note that this brain, in its simplicity of convolution, is much more like that of 

 foetal dogs than of any adult recent species. Among existing carnivora, we find 

 such simple sulci approximated only in some of the smaller viverrines and mustelines. 



