PETERSON: A REVISION OF THE ENTELODONTIDA 51 
“T+ relatively large, upper canines much elongated and pointed, M+ with well 
developed cingulum externally, M? with cingulum faintly developed externally, 
and M® with cingulum developed only on the antero-external angle. Lower canine 
rather short, which may be due to the fact that the specimen pertains to a rather 
young, though adult individual. Lower premolars high and sharply pointed ; 
molars with high anterior tubercles. Mg with an unusually prominent posterior 
basal heel.’ Cingulum only fairly indicated on the external faces of the inferior 
molars.” 
Archeotherium crassum (Marsh). 
Type: Fragments of a skeleton. 
Locality : Eastern Colorado. 
Horizon: Lower Oligocene (‘Titanotherium beds). 
Locality of Type: In Collection of Yale Museum, No. 12020. 
In 1873 Professor Marsh founded this species on fragments of a skeleton (58a, 
p. 487). It was apparently the first time that the characteristic dependent process 
of the jugal of the American forms of the Entelodontide had been observed, and 
Marsh compared this process with those on the zygomatic arch in some Edentates 
and Marsupials. Marsh also pointed out that the radius and ulna of this species were 
separated or very loosely united.* Some idea of the foot structure of this species was 
also derived from this specimen. In a later paper (68, p. 408) Marsh more fully 
describes the type, together with additional material collected in Colorado, South 
Dakota, and Nebraska. On Plate VIII of this publication Marsh figures the skull 
and feet, which he regards as belonging to A. crasswm, and states that the dependent 
process of the jugal ‘(extends downward to the inferior margin of the lower jaw in 
front of the angle. This is the case when these processes are somewhat expanded 
transversely, as shown in figures 2 and 8, which represent the skull as it lay 
in the matrix” (see fig. 8). Marsh also calls attention to the small brains, the struc- 
ture of the feet, and to the protuberances on the inferior border of the lower jaw, of 
which the anterior pair is slightly the heavier. In 1894 Marsh published the res- 
toration of A. crassum (64, pp. 407-408, Pl. IX) and finally in 1897 published the 
same restoration (65, Pl. XXX) with the legend Entelodon crassus. In the text 
of the same volume, pp. 522-528, Marsh also referred to Archexotherium as Entelodon.® 
Through the courtesy of Professors Schuchert and Lull of Yale University the pres- 
"The posterior position of the chin-process, the high anterior tubercles of the lower molars, and the prominent 
basal heel of Mz are among the more important characters of this subspecies. 
* This is probably true of nearly all the species from the lower beds. 
®° This indicates that Marsh had already obtained some information which led to Miss Lucy P. Bush’s publication 
of a later date in the American Journal of Science (Series IV, Vol. XVI, pp. 97-98, 1903). 
