THE MAMMALIA OF THE UINTA FORMATION. 555 



calcaneuin so that the tibia articulates with the latter in Diplacodoa and Tllanolhe- 

 ritun. The fibiilo-calcaneal facet in Pala'osyops increases to a considerable size in 

 Titanothevlum. The cuboid and other elements of the second row of tarsals are 

 rather l)road. The metatarsal articulation is secondarily of the alternating type. 



Pahvosyops. The astragalo-calcaneal facets together present a broad surface for 

 the cuboid and navicular, between the bones is a gap which is bridged b}' the cuboid. 

 The astragalo-cuboid facet is slightly nari-ower behind than in front. The c a 1 c a - 

 n e u m has a small fibular facet, and distally presents a broad oval face for the cuboid. 

 The cuboid is subquadrate in proportion, much as in the tapir sei'ies, and presents a 

 sharply defined astragalar facet ; distally it rests upon mt. iv, and presents a variable 

 facet anteriorly for mt. in. The ectocuneiform is also subquadrate anteriorly and not 

 only suppoi'ts mt. iii, but has a broad facet laterally for mt. ii. The mesocuneifoim is 

 thus somewhat llattencd. The entocuneiform is not preserved in the Princeton 

 collection. 



Dijdacodon. The tarsus (Plate YIII ) is represented merely by an astragalus 

 and calcancum which are somewhat crushed, but nevertheless present impoitant 

 transition characters. Thus the filnilo-calcaneal facet is much larger ; the tibia ex- 

 tends from the astragalar troehUa upon the calcancum ; the tuber calcis is very long 

 and laterally compressed. In the astragalus the trochlea is dee}); the three cal- 

 cancum facets are nnu h reduced ; the cuboidal facet is broader anteriorly and nar- 

 rower posterioily. There is thus an intermingling of Pahvosijops and TUanothen'um 

 characteristics. Viewed together, however, the.se bones are elevated and laterally 

 compressed, indicating a high and rather narrow pes. With the metacarpals above 

 described, we may infer that Diplacodon had gained greatly in height upon Pakfio- 

 st/ops without having acquired any of the massive proportions of TlUtiiotlierium. 



Titfinotheyiinn. The tarsus is veiy broad and fiat, tlie metapodials spreading 

 widely. lathe astragalus the trochlea is shallow, the inferior calcaneal facet is 

 greatly reduced and is confluent witli the cuboidal facet; the latter is broad in front 

 and tapers to a point posteriorly. The gap between the astragalus and calcancum, 

 observed in Ptdipoyiyops, is here greatly enlarged, the cuboidal contact with both as- 

 tragalus and calcancum is intcirupted by slight surface depressions, analogous to tlie 

 "navicular fossa" in the horse. The tibia and Hl)ula both have calcaneal facets. By 

 the broadening of the cuboid the navicular is greatly rcdiu-ed. 'i'lic cuneiforms are 

 ttattencd. Mt. in has a bioad contact with the cuboid, ami ml. ii with the ecto- 

 cuncilbrm. 



