THE MAMMALIA OF THE DEEP K1VEH BEDS. 171 



in the median line, above the foramen magnum, is a wide convexity bounded on each 

 side by a shallow fossa. Towards the summit of the inion this convexity passes 

 into a shallow concavity with a faint median keel, inclosed between processes of the 

 supra occipitals and parietals. These processes are broken away in the specimen, so 

 that their length cannot be determined. Apparently, however, they were not so long 

 and prominent as in B. borealis, in which the occiput is utterly unlike that of any 

 existing ruminant and has more the peculiar shape characteristic of the Oreodontidm. 

 Neither Filhol nor Fraas give figures of this region of the skull in Palceomeryx, but 

 Dicroceros has an entirely different occiput (see Filhol, ISTo. 13, PI. XXXIV, Fig. 4) 

 which is broad and low and forms a nearly vertical plane. 



The paroccipital processes in Blastomeryx are long, laterally compressed, and 

 broad at the bases, which are closely applied to the tympanic bullae. Between the 

 condyle and the paroccipital process the inferior surface of the exoccipital displays a 

 large, deep fossa, which is much larger and more deeply impressed than in Antilo- 

 cajwa, and the process stands much more in advance of the condyle than in that 

 animal. The mastoid is exposed upon the surface of the skull and forms quite an 

 area between the squamosal and exoccipital ; its lower end forms a dense rugose 

 mass, though there is no proper mastoid process. The relations of the mastoid are 

 very much the same as in the prong-buck, except that it is more advanced in front 

 of the condyle in position and descends lower upon the paroccipital process. The 

 cranium is long and quite full and rounded, though more slender and less capacious 

 than in Dicroceros. The parietal zone is very long and roofs nearly the entire cranial 

 cavity; obscurely marked temporal ridges pass backward from the bases of the horns 

 and converge to form a low but distinct sagittal crest, which is longer than in the 

 European genus. The postorbital constriction is not strongly marked, though much 

 more so than in the existing genera of horned ruminants. The squamosal is very 

 large and makes up nearly the whole side wall of the cranium ; the root of the zygo- 

 matic process forms a thin, depressed plate, which is much extended in the antero- 

 posterior direction and is pierced by a large venous foramen. The zygomatic arch is 

 slender and depressed, and though the distance from the postglenoid process to the 

 last upper molar is nearly the same as in Aniilocapra, yet, owing to the more ante- 

 rior position of the orbit, the zygomatic arch is considerably longer than in the 

 modern genus. The glenoid cavity is thoroughly ruminant in character, though the 

 anterior convexity and posterior concavity are more decided and the postglenoid 

 process somewhat longer than in the prong-buck. The tympanic bullae are small 

 and of the shape usual in the antelopes, with a deep groove for the attachment of 



