MUSEUM OF COMPARATIVE ZOOLOGY. 77 



The Skull. 



A little of the superior wall of the cranium is preserved in one of the speci- 

 mens, which probably belonged to a young animal, as the horn is a mere rudi- 

 ment. The frontals are extended back of the orbits and form a considerable 

 part of the cranium, but they are shorter than in Cariacus. Distinct though 

 not prominent ridges converge from the back of the orbits, and probably unite 

 behind in a sagittal crest, though as this part of the cranium is broken away 

 the existence of a sagittal crest cannot be certainly affirmed. If present at all, 

 it must have been a mere indication. The orbits are large, and have sharp su- 

 perior borders. In Cosoryx and Antilocapra the horn arises directly over the 

 orbit, and the same is probably true of the John Day species of Blastomeryx ; 

 but in the Loup Fork species of the latter genus the base of the antler has 

 shifted its position somewhat, so as to spring from the posterior portion of the 

 orbit, and it is also directed obliquely backwards, which apparently is the be- 

 ginning of a process which results in the position of the pedicels observed in 

 Cariacus. So much of the frontals as is preserved shows no trace of any sinuses, 

 only the ordinary diploetic structure of the cranial bones. The bases of the 

 antlers are much farther apart than in the deer, and are not connected by any 

 intervening ridge. The coronal suture is nearly straight. As usual in rumi- 

 nants, the parietals have coalesced into a single large bone, which clearly makes 

 up most of the roof of the cranium. In the anterior portion the supra-orbital 

 ridges are carried over from the frontals and converge to a point. Only the 

 anterior part of the parietal is preserved. The inferior surface of this, and of 

 the frontals as well, is deeply channelled by the winding and complex cerebral 

 convolutions. Of the dentition we possess only a superior molar, and several 

 inferior molars of a smaller species. The upper molar is very cervine in struc- 

 ture. The crown is brachyodont, and nearly as broad as long, while in Cosoryx 

 it is strikingly narrow as well as hypsodont. The valleys are deeper and the 

 external crescents more flattened than in Palceomeryx, while the internal cres- 

 cents are somewhat simpler. The cingulum has almost disappeared, but a small 

 basal pillar occurs between the inner lobes, as in many deer. The lower mo- 

 lars have low and rather narrow crowns ; the valleys are shallow, and disappear 

 after a comparatively short time of attrition. The cingula are but faintly indi- 

 cated. As compared with the molars of Cariacus, those of Blastomeryx are 

 simpler in the uncomplicated inner crescents of the upper teeth and the shal- 

 lower valleys. 



The Skeleton. 



The scapula is much like that of Cosoryx, though with some difference, the 

 neck is more contracted, the coracoid more prominent, and the acromion more 

 overhanging. The glenoid cavity is small, nearly circular in shape, and quite 

 deep ; the anterior or coracoid border is thin and curved, the glenoid border 

 much thickened and nearly straight. The spine is not very high and divides 

 the blade into unequal fossse, the postscapular being much the larger, and the 

 acromion overhangs the neck, but does not nearly reach the margin of the 

 glenoid cavity. 



