102 Bulletin. American Museum of Natural History. [Vol. XXXIV, 
‘less be an additional argument for this theory. But I do not think the 
theory should be bolstered by unsound evidence, and as such I am compelled 
to regard this reference. 
Briefly, the bone is not Hyenodon nor closely related thereto, but it 
might represent some other genus of Hyenodonts, known or unknown, or, 
less probably, some genus of Miacide or of Fissipedia or some other 
Creodont or Pinniped family. Since there are no clearly defined characters 
at present known distinctive of the carpal*bones in the several families, 
as such, of Creodonts and early Carnivora, it is not possible to refer this 
bone with certainty to any one family. The probabilities stand as stated 
above. 
One thing however may be stated with certainty. The bone is not 
Pachyena, Dissacus, Mesonyx or Synoplothertwm, nor is there any valid 
evidence for referring it to Pale@onictis. 
Hapalodectes Matthew 1909.! 
Type, H. leptognathus from the Wasatch, Wyoming. 
Generic characters: Dentition ?°0.1.4.3; jaw slender, teeth highly compressed, 
metaconids small, paraconids well developed on m;—ms, talonids high, sharp, tren- 
chant. 
The species referred to this genus are represented by lower jaws only» 
the upper dentition, skull and skeleton being unknown. They are of much 
smaller size than other Mesonychide, and the knife-like teeth are unworn 
in any of the specimens. They do not show any indications of shearing 
action. 
Hf. compressus Matthew is distinguished by the more slender jaw and 
somewhat greater compression of the teeth, characters more marked in 
referred specimens from the Lost Cabin horizon than in the type which is 
from the Lysite. 3 
Seven lower jaws altogether are referred to the genus, two probably 
Gray Bull, one from Lysite of the Big Horn, three from Lysite of the Wind 
River Basin, and one from the Lost Cabin horizon of the Wind River. They 
show a progressive slenderness of jaw and greater compression of the teeth. 
|Hapalodectes leptognathus (Osborn 1892). 
Dissacus leptognathus Osporn (& WortMAN) 1892, Bull. Am. Mus. Nat. Hist., 
Vol. IV, p. 112, fig. 10; (Hapalodectes) Marrunw 1909, Mem. A. M.N.H., vol. IX, p. 
tO. 8. GS; Bulk 361): 93, 
