the mammalia of the uinta formation. 563 



5. The Paljeosyops, Diplacodon, Titanotherium Series. 



The general characteristics of the feet in this series arc the following: The car[)iis 

 is broad and llat, and the lateral displacement is limited; there arc four spreading and 

 fully functional toes. In the pes on the other hand the cuboid extends rapidly 

 beneath the astragalus, the lateral displacement being very rapid. The calcaneura 

 lias a fibular facet. The terminal phalanges arc flat and spreading distally. 



Carpus. In each of the carpal elements in the genera of this series we invari- 

 ably find (excepting in tlie hinai- of some of the Bridger species) that the transverse 

 diameter exceeds the vertical, in a ratio increasing as Ave ascend. The lunar can 

 always be recognized by its nearly subequal magnum and unciform facets, and the 

 unciform by its broad facet for mc. \. 



Pakfosyops (No. 10,013, Princeton Coll.). There are two distinct types of 

 feet which may be here referred to Palceosi/ops, but cannot with certainty be deter- 

 mined specifically. One belongs to a large and heavy form with short, stout digits 

 (possibly 7^ major Leidy, or P. validens Cope), the other to a lighter, more graceful 

 animal witli long, rather slender digits (possibly P. pahidosus Leidy). There is a 

 third type, intermediate in size, between the above, but showing the heavy propor- 

 tions of the large type. The scaphoid has subequal magnum and trapezoid 

 facets, and, in its somewhat oblique position, transmits its weight equally to both 

 elements. The lunar has a dee]) radial facet; it is wedge-shaped inforiorly ; the 

 direction of its magnum and unciform facet varies in the two types from a sharjier 

 to a more obtuse angle ; thus, in the lighter forms the magnum facet is small and 

 strongly inclined, Avhile in the heavy forms the same facet is larger and more horizon- 

 tal ; corresponding variations are found in the superior facets of the magnum; 

 taken together they determine the degree of transmission of the weight through the 

 magnum and uncifoim I'cspcctively. The t r a p e z i u m sustains no direct pressure, 

 but ailiculates with the scaphoid, trapezoid and mc. ii. The trapezoid receives 

 half the weight of the scaphoid. The u nci form is \ei\ broad, resting inferiorly 

 upon the mc. ni-v. The variation^ in the metapodials between the heavy and slender 

 types are stiongly marked. 



Diplacot/iiit. The scaphoid, lunar and cuneiform of a carpus have been collected 

 from the Uinta which agree so closely with the corresponding elements in the slender 

 type of Pahiiosijops above described, that they require no further description. They 

 belong either to a small sjiecics of Z'/yj/rtcoc/w^, much smaller lliaii the iKdalnsoi 

 Marsh, or to a persistent species of Pnhwsijops. The only departure from the above 



