Marsh Collection, Peaoody Museum. 439 



squamosals exhibit about the same relations as those of the 

 dog, with the possible exception that the squamosal is larger. 

 The parietal foramina, which in this region form such a con- 

 spicuous feature of the skulls of so many of the Creodonts, 

 are very small ; in fact, in the specimen under consideration, 

 the one on the right side is practically absent. 



The lambdoidal crest is only moderately developed, showing 

 about the same degree of elevation as that seen in the living 

 insectivorous genus Gymnura, which the superior and occipi- 

 tal portions of the skull resemble somewhat closely. The 

 occiput is not very broad, and rises almost vertically to the 

 plane of the long axis of the skull. It overhangs the condyles 

 but very slightly, in marked contrast with its great backward 

 projection in some of the Creodonts. The condyles are 

 relatively very large, obliquely placed, and well separated. 

 In comparison with those of a red fox, in which the size of 

 the two skulls agrees very well, the occipital condyles of 

 Sinopa are quite one-third larger. The extent to which the 

 mastoid portion of the periotic is exposed upon the postero- 

 lateral wall of the cranium cannot be made ont with certainty, 

 but it appears to be very little, if any. 



The base of the skull is in a state of excellent preservation, 

 and its anatomy can be quite fully determined. The basi- 

 occipital is broad, and at the point of its articulation with the 

 basisphenoid exhibits two prominent tubercles, separated by a 

 longitudinal groove. The office of these eminences, which are 

 roughened for muscular attachment, was doubtless for the 

 origin of the recti capili. The paroccipital is large, consider- 

 ably flattened from above downward, and has a very marked 

 outward and backward direction, as in the Insectivora. Just 

 how much of this, however, is due to crushing, it is difficult 

 to say, but it appears to be natural. The mastoid, which is 

 separated from the paroccipital by a groove, is prominent, as 

 in the Marsupials. The petrosal portion of the periotic is not 

 covered by any tympanic bulla below, and if a tympanic bone 

 were present it was not attached to the skull. There are, 

 moreover, no expansions of the alisphenoid contributing to the 

 formation of an otic bulla, as is so frequently the case in the 

 skulls of the Marsupials and Insectivores. The petrosal por- 

 tion of the periotic, when seen from below, appears as a small 

 rounded eminence, near the outer posterior extremity of 

 which, in a deep transverse groove, is seen the opening of the 

 fenestra rotunda. In the Carnassident skull, this transverse 

 groove is absent, and the opening of the fenestra is larger and 

 somewhat tubular in appearance. Above, and anterior to this, 

 is seen the opening of the fenestra ovalis, into which the base 

 of the stapes is received. The absence of any groove leading 



