PETERSON: A REVISION OF THE ENTELODONTIDA 67 
Locality of Type: The Carnegie Museum (Catalogue of Vertebrate Fossils, No. 
1594). 
Principal Generic Characters of Dinohyus : Median incisor reduced and some- 
times wanting. Transverse diameter of P2 nearly equal to the antero-posterior, P; 
with large deuterocone ; the crown subquadrate in outline and the tooth of rela- 
tively small size; a tendency to increase the antero-posterior diameter of M*, and 
the meta- and hypocones of relatively large size; lower molars with subequal 
height of posterior and anterior tubercles ; the tubercles separated by narrow cross- 
valleys; the trigon lost; all the premolars spaced ; dependent process of the jugal 
of proportionally small size and the posterior termination of the zygomatic process 
developed into a strong buttress at the anterior border of the glenoid cavity ; 
small bony eminences on the chin and a strong knob-like process on the inferior 
border of the ramus opposite P;; a relatively gradual backward slope of the angle ; 
relatively short alveolar border of the premaxillary and rather short chin; verti- 
cal and transverse canals of the dorsal vertebree as in Sus; fibula codssified with 
the tibia; trapezium absent and mt. V sometimes absent. 
Genus AMMODON Marsh. 
Although Professor Cope (5, p. 704), Leidy (50, p. 388), and Marsh (57, p. 3), 
referred to the New Jersey specimen, there was no adequate description of the type 
until 1898, when the latter author gave a short description together with good illus- 
trations (63, pp. 409-410). 
Known Generic Characters of Ammodon: P4 of relatively large size ; large hypo- 
conulid on M;; anterior and posterior tubercles of lower molars subequal in height ; 
the logs of the trigon; cross-valleys narrow ; type representing an animal of large 
size. 
Ammodon leidyanum Marsh. 
Type: Pz; Neotype: My, of left” side. 
Horizon: Middle Miocene ? 
Locality: Near Farmingdale, Monmouth County, New Jersey. 
Locality of Type: Collection of Yale Museum, No. 12040. 
From Marsh’s description (68, pp. 409-410) and also from my observations 
upon the specimen it seems quite probable that Pz and My which Marsh described 
belong to the same individual. Working on this hypothesis it would seem 
that Pz is of greater proportionate diameter than in Dinohyus hollandi. The poste- 
rior heel of Pz in Ammodon is also larger than in Dinohyus, which is due to a heavy 
25 Professor Marsh mistook the left M; for that of the right side, a mistake which might lead to confusion. 
