Cope.] •"* [August 15, 



From these, and inferentially from other specimens, is derived the curi- 

 ous fact, that there are four distinct metacarpals, all supporting digits, 

 while there are but two metatarsals, which are coosified into a cannon 

 bone. This diversity between the limbs is unparalleled, although an 

 approach to such a condition is seen in the peccary. In this animal, as is 

 well known, there are four distinct digits in the manus, while in the pes, 

 the metatarsals are coossified proximally, and the fifth metatarsal is re- 

 duced to a scale. This difference between the two limbs is a further 

 illustration of Mr. Ryder's statement that the posterior limb is in advance 

 of the anterior in grade of development, for which I have endeavored to 

 account by reference to the fact that it is the posterior foot which receives 

 the greater number of impacts in progression. This is because the hind 

 limb is the principal propeller of the body. 



In accordance with the structure of the feet, the fore-limb is much be- 

 hind the posterior limb in the .fixity of its parts. The ulna and radius 

 are distinct ;' the head of the latter a regular transverse oval. The distal 

 extremity of the fibula is not coossified with the tibia, but forms a sepa- 

 rate bone, as in the Ruminantia. 



The lunar is mainly supported by the unciform, so much so that the 

 front face of the magnum is not beveled to fit the former. Behind the 

 face, the edge of the magnum is a little beveled for the lunar ; but the 

 former bone lies almost entirely under the scaphoid. The trapezoides is 

 coossified with the magnum. No distinct trapezium. 



The cuboid and navicular are solidly united. The ecto- and mesocu- 

 neiforms are distinct, and there is no entocune'iform. The second metatar- 

 sal is represented by a fiat oval bone which is borne on the underside of 

 the projecting heel of the third metatarsal. The fifth is of smaller size, 

 and is a scale imbedded in a depression of the posterior part of the side of 

 the fourth. Ungues unilateral, trihedral and acute. 



Hypertkagxjlus Cope. 



Remains of this genus are as abundant in the White River beds as are 

 those of Leptomeryx, and like that genus I know but ihe one species, the 

 H. calcaratus Cope. Unfortunately I have not been able to obtain bones 

 of the skeleton connected with dentition from this formation, although 

 numerous bones occur separately which probably belong to it. The 

 genus is however abundantly represented in the John Day Miocene beds 

 of Oregon, where Leptomeryx does not probably occur. At least no 

 specimens of the latter are to be found in a collection of between one and 

 two hundred individuals of this general type in my collection. I cannot 

 distinguish the John Day species from the H. calcaratus, although the 

 size is generally distinctly larger.* In other cases the size is the same. 

 To the John Day specimens then I refer for the characters of the feet of 

 this genus. 



* It is probably this species that is cited by Leidy as the Leptomeryx evansi iu 

 the Report U. S. Geol. Survey Terrs. I, p. 216. 



