100 R. S. Lull — New Tertiary Artio dactyls. 



ample in development, as were apparently those of the 

 sense of smell. The cranial cast displaces 45 cc. of water : 

 estimating the specific gravity as approximately 1, it 

 would give a brain weight of ca. 45 grams or iy 2 ounces. 

 Further detailed description is rendered unnecessary 

 by the figures, in which the size, identifiable fissures, and 

 foramina are indicated. 



Mandible. 



Mandibles representative of more than twenty in- 

 dividuals are present in greater or less degree of perfec- 

 tion. They pertain to individuals of varying age, from 

 very young with milk dentition to aged animals whose 

 teeth were badly worn. The ramus is rather slender, 

 though proportionately less so than in Antilocapra, and 

 the shape of the jaw from below the third molar to the 

 angle varies as well, as the figures show, that of Aleto- 

 meryx lacking the peculiar cut-away appearance of 

 the prongbuck. Thus the whole ascending portion of the 

 ramus is relatively much broader in the fossils, and the 

 coronoid process is more erect. This is in harmony with 

 the longer and more primitive cranial portion of the 

 Aletomeryx skull. The anterior part of the mandible 

 changes form somewhat with age as with Antilocapra, 

 the rami becoming more slender just behind the symphy- 

 sis. The symphysis itself also lightens, for in the 

 younger jaws the presence of both milk and permanent 

 incisors, the latter in process of formation, necessitates 

 a greater volume of containing bone. The mental fora- 

 men lies just behind the after symphysial limit ; the man- 

 dibular foramen, which is on the inner face of the ascend- 

 ing process, lies at about the upper level of the teeth in 

 the older specimen, about their mid-height in the younger 

 jaws. 



Four alveoli are present at the anterior end of each 

 ramus for the three incisors and the incisiform canine 

 which forms an integral part of the cropping series. In 

 jaw No. 10754 the uncut I 3 and canine are present, in 

 another fragmentary symphysis, I 2 and 3 . The unworn 

 tooth crowns as they appear are spatulate with entire 

 rounded margins quite comparable to those of Antilo- 

 capra. They may have been somewhat more procumbent. 

 Several loose incisors are present in the material, but 

 none that were in use are in position in an}^ of the jaws. 



