PETERSON: THE AMERICAN DICERATHERES. 429 



has the ventral keel of the same proportions as in the smaller species, and the same 

 faintly indicated neural spine, and the strong transverse process similarly expanded 

 lateraUy. Cervical four has the neural spine as prominent, but the back part of 

 its transverse process is perhaps somewhat heavier than in D. cooki. Cervical six 

 again has the same downwardly directed inferior lamella of the transverse process, 

 which is, however, proportionally less developed fore-and-aft than in D. cooki. 

 The dorsal vertebra referred to presents the same characters as the corresponding 

 bone in the latter species, including the mammillary process on the upper anterior 

 surface of the transverse process. With the exception of a somewhat more de- 

 cided ventral keel and possibly a lighter spine, the lumbar series associated are of 

 approximately the same relative size and detailed structure as in the smaller form, 

 D. cooki. 



The remains of the limb-bones (No. 1910) which were found in this same 

 quarry, and are provisionally associated with the type of D. niobrarense, show that 

 the scapula is proportionally shorter than in the smaller species, and possibly also 

 somewhat broader; the coraco-scapular notch shorter and shallower; the bicipital 

 groove of the humerus smaller; and the shaft of the ulna straighter. The propor- 

 tionate length of the femur cannot positively be ascertained from the material at 

 hand, but the tibia is decidedly shorter. The remains of the foot-bones asso- 

 ciated bear no marked differences from those of D. cooki, except their larger size. 



The type (No. 1040) of " Metacoenopus" (Aceratherium) stigeri in the Amherst 

 College Museum is described by Dr. Loomis, and the right upper molar-premolar 

 series is illustrated. Dr. Loomis says: "The small skull is elongated, light in 

 build and rather narrow. The orbit is large and the zygomatic arch light. The 

 premolar teeth are crowded, there being neither an anterior nor posterior cingulum, 

 though one is developed along the inner face around the protocone, running out 

 on the hypocone. Crista and crochet are wanting on these teeth of a rather old 

 individual, except that on the fourth premolar there is a faint trace of a crista, 

 and on the third premolar a small antecrochet is developed. On the molars the 

 cingulum is reduced as in the premolars, and both crochet and crista are wanting. 

 The protocone, however, is swollen, making a considerable fold as in European 

 Diceratheres. A. stigeri is closely related to A. egrerius but is smaller, and has 

 the cingulum on the premolars and the crochet on the molars less developed." 



In the description of this complete skull the greatest stress is laid on the 

 configuration of the grinding surface of the teeth, principally for the purpose of 

 comparison. The illustration indicates an animal of old age, as Loomis states. 

 The crista, if there was one, has consequently disappeared by wear. The crochet 



