432 MEMOIRS OF THE CARNEGIE MUSEUM. 



to form a sagittal crest, but continuing separate to the inion where they join the 

 lambdoidal crest." Loomis on the other hand states that the skull is relatively 

 short and high, with high occipital crest and a moderate sagittal crest, formed by 

 the confluence of the two ridges from over the orbits. This mistake is undoubtedly 

 due in part to the illustration (Ann. Cam. Mus., Vol. IV, 1906, p. 48, Fig. 12) 

 which does not accurately represent the top of the skull. This is remedied in the 

 illustration given with this paper, PL LXII, Fig. 1. 



Loomis further states that "on the premolars, the cingulum is greatly reduced, 

 while the strong crochet is united with the feeble crista, thus isolating the median 

 fossette. In like manner on the molars the cingulum is reduced to traces on the 

 front, inner side, and rear of the teeth." While this description was undoubtedly 

 based on the material in the Amherst Museum and answers some individuals of this 

 species in the Carnegie Museum, the type specimen does not agree with his de- 

 scription. In the first place the internal faces of the premolars, except P- are 

 incomplete. The said premolar has a prominent cingulum on the anterior and 

 internal faces of the protocone, which is confluent by wear with the grinding 

 face of the metacone. On the antero-internal angle of P'' a prominent cingulum 

 is indicated, the inner face of the tooth is otherwise, as stated, broken off as is 

 also P* on the anterior inner angle (See PI. LX, Fig. 1.) M^ and M^ are also dam- 

 aged in this same region, but enough is preserved to indicate that the cingulum 

 is as prominent as is the case in other skuUs, which are more complete in this 

 respect. P- and P'* have the crochet united with the ectoloph through wear; 

 no crista is shown, while the post-fossette is entirely isolated on P\ P"* has only a 

 trace left of the crochet, but no crista; post-fossette nearly enclosed. M' has 

 crochet united with the ectoloph by wear, and post-fossette enclosed. M- has a 

 strong crochet and the crown is injured in the region of the crista. M^ has a 

 strong crochet and a fairly prominent crista. The entire dentition is much worn, 

 plainly indicating an old individual. The distinguishing characters of Acera- 

 therium stigeri and Diceratherium schiffi given by Dr. Loomis now appear to rest 

 entirely on sexual characters and individual variation, the type of his proposed 

 species being female skulls of D. cooki, while his species D. aberrans is established 

 on D. P.^ of the left side as has already been pointed out.-'^ 



From Professor Barbour's description and figures of his proposed species 

 D. arrikarense in Science, N.S., Vol. XXIV, 1906, p. 780, it is clear that he has 

 described a male skull of D. cooki minus the dentition, while Mr. Cook's proposed 



"Peterson, 0. A., "Recently PiMpdsed Specie.? of the Genus Diceratherium," Science (N.S.), Vol. 

 XXXVI, 1912, p. 801. 



