MUSEUM OF COMPARATIVE ZOOLOGY. 99 



resemble in this respect those of R. ticliorhinus. Briefly stated, in all living 

 forms the protoloph is simple, and the accessory folds are developed, first from 

 the metaloph, then from the ectoloph ; while in the known extinct American 

 forms the ectoloph is simple, and the protoloph develops a fold to which a fold 

 of the metaloph is sometimes superadded. 



In view of these facts, together with the numerous divergences in the skele- 

 ton, there is strong corroboration for the opinion advanced ^ by Scott in 1883, 

 that Aphelops should not be regarded as ancestral to any of the recent foreign 

 species, but rather as the last kno^\•n of an extinct American series. The ques- 

 tion is still an open one whether its distribution was confined to this continent. 



CHALICOTHERIOIDIA.2 



CHALICOTHERIUM, Kaup. 



Specimens of this genus are rare in American formations, and have not as yet 

 been reported from the Loup Fork. Marsh ^ has menti(jned the occurrence of 

 it in the John Day Miocene of Oregon, and in view of the discoveries of Fors}i;h 

 Major and Filhol, it is altogether probable that the foot-bones from that for- 

 mation, which Marsh has referred to the Edentata under the names Moropiis 

 distans and M. senex,* belong to the same genus. A third species of the same 

 genus is announced by Marsh ^ from the Loup Fork, M. elatus, which is prob- 

 ably represented in the Garman collection from the Loup Fork of Nebraska. 



Chalicotherium elatum? Marsh. 



(Syn. Moropus elatus, ]\Iarsli.) 



The specimen is a portion of a right superior maxillary containing the third 

 and fourth premolars and the first molar. The premolars have a flattened ecto- 

 loph connected by two convergent crests, with a large internal cone which is 

 cleft at the summit ; the base of this cone is surrounded by a strong internal 

 cingulum. The ectoloph is worn by two symmetrical incisions alternating with 

 the transverse crests in the third premolar, Ijut in the fourth these incisions are 

 asymmetrical. The first molar is partly of the Titanotherium type, with its 



1 E. M. Museum Bulletin, No. 3, 1883, p. 17. 



2 Gill, Arr. of tlie Fam. of Mammals, Smillisonian Misc. Coll., Xo. 2.".0, p. 271. 

 This order was properly flefincd by Gill, but was erroneously placed mong the 

 Artiodactyla, owing to the reduced condition of the superior incisors. Filliol's forth- 

 coming memoir upon tlie Mammals of Sansan will probably enable us to determine 

 its phylogenetic relations. 



3 American Journal of Science and Arts, 3d Series, Vol. XIV. p. 362. 

 * Ibid., pp. 240, 250. 



5 Ibid., pp. 2.30, 2.M. 



