LEPTOCERATOPS GRACILIS 79 



and fibula, the right by the femur only. The caudals are intermittently present. Except for the 



hind feet, of which only a few phalanges are preserved, and parts of the skull, this specimen has 

 been restored completely from the type specimen, ;ind is to be mounted. Hence, it affords an admi- 

 rable basis for comparison with Protoceratoops, its nearest ally. With Brachyceratops, on the other 



hand, there is little basis for comparison; nevertheless, as such comparison has been made, it is well 

 to discuss here the points of contrast. 



The skull of Leptoceratops has little in common with Brachyceratops. The latter has a large 

 nasal horn composed of a right and a left element divided by suture, the entire structure, with the 

 exception of a small terminal ossicle, being a continuation of the nasal bones. In Leptoceratops, there 

 is no trace of a nasal horn, the nasals, wide at their posterior end, terminating in a point, with no 

 elevation of profile or other indication of even an incipient nasal horn. The supraorbital horns, 

 which are present, though small, in Brachyceratops, are also presumably absent in Leptoceratops, 

 although of this there is no direct proof. Other skull details, available for comparison, lie in the 

 crest, mandible, and teeth. In Leptoceratops, the posterior median part of the crest (parietal) only 

 is preserved. It differs from that of Brachyceratops in the form of the hinder margin, which in the 

 former is straight, in the latter with a shallow reentrant angle. Leptoceratops has a rather high, thin 

 sagittal ridge extending nearly to the posterior edge; Brachyceratops has none, although the midline 

 is somewhat elevated, with the undulating profile which is characteristic of several ceratopsian genera, 

 notably Monoclomus {crassus), and Triceratops. Judging from the position of the squamoso-parietal 

 suture, the squamosals in Leptoceratops must have extended to the rear of the crest; in Brachycera- 

 tops, the same evidence indicates that they were short, and terminated at about the middle of the 

 lateral margins. Finally, there is no evidence whatever of the presence of parietal fenestrae in the 

 preserved portion of the Leptoceratops crest. They were present, but apparently small, in Brachy- 

 ceratops. This, however, may be only a difference of degree and not of kind, for all other Edmonton 

 Ceratopsia possess these openings, and Leptoceratops may have. The mandible and predentary 

 differ markedly, those of Leptoceratops being short and deep, with an unusually large predentary in 

 proportion to the dentary. In Brachyceratops, the mandible is slender and the predentary relatively 

 small, more as in normal ceratopsians. Alveoli in the premaxillary of Leptoceratops betray the pres- 

 ence of premaxillary teeth which certainly do not occur in Brachyceratops. Apparently, Leptocera- 

 tops has single-rooted teeth, those of Brachyceratops being probably of the regular ceratopsian bifanged 

 sort, although this cannot be verified. 



Among skeletal contrasts there are marked differences in the ilia, pubes, ungual phalanges, and 

 in the spines of the caudal vertebrae, all of which are typically ceratopsian in Brachyceratops and 

 differ widely from those of Leptoceratops, in which these elements are highly diagnostic, as the 

 comparison with Protoceratops will show. On the whole, I see no indication whatever of relationship 

 between Brachyceratops and Leptoceratops, the latter being something very much apart from the 

 remainder of the American Ceratopsia. 



Mr. Brown has already stressed a number of points of comparison between Leptoceratops and 

 Protoceratops, and the newly acquired skeleton, instead of showing distinctions, serves only to empha- 

 size further likenesses which indicate real relationship between the genera even though they were 

 remotely removed from one another in space. Several instances of such discontinuous distribution 

 are known, however, notably the extant Tapirus, the surviving members of which, living as they do 

 in Brazil and the Malay peninsula, are yet more remote. 



So far as the skulls of Leptoceratops and Protoceratops can be compared, the similarities include 

 hornlessness, the presence of premaxillary teeth, the single-rooted character of the other teeth, and 

 a general agreement of size on the part of some of the larger Protoceratops skulls. The lower jaws 

 agree somewhat in shortness and depth, but the form of the coronoid differs, as does the proportionate 

 size of the predentary bone, which is much the larger in Leptoceratops. 



The parietals are alike in the possession of the sagittal crest, and in the comparatively straight 

 posterior border, but there the resemblance ceases, for the squamosal sutures are much farther apart 

 in Protoceratops, where they form a wide angle of about 90° with each other, while in Leptoceratops 

 they are more nearly parallel, thus implying a short squamosal on the part of the former, and a long 



