„ TRANSACTIONS OF WAGNER 



UINTA SELENODONTS 



compressed, is quite thick ; anteriorly the ilium expands into a broad, everted 

 plate, with rounded and simple crista. The acetabulum is large and deep. 

 Both ischium and pubis are broken away, but the section of the former shows 

 that the spine or crest was low and inconspicuous. 



The femur is likewise very tylopodan in appearance. It is considerably 

 longer and stouter than the humerus, equalling the tibia in length. Proxi- 

 mally, the bone is broad and carries a large, ovoidal head, set upon a short 

 neck, and a rather low great trochanter, which does not rise quite so high as 

 the head. The shaft is heavy, elongate, arched forward, and of nearly uniform 

 diameter, except at the distal end, where it is somewhat broadened and 

 thickened. The condyles are rather small and unequally developed, the ex- 

 ternal one projecting more behind the plane of the shaft. Above the outer 

 condyle is quite a deep pit for the attachment of the plantaris muscle. The 

 rotular trochlea is asymmetrical, owing to the prominence of the inner 

 border, and above the trochlea the dorsal face of the shaft is grooved. In 

 Poebrotherium the femur is very much like that of the Uinta genus, but has a 

 somewhat higher great trochanter, a larger pit for the plantaris, a wider 

 trochlea, and much more prominent condyles. In Leptomeryx also the proxi- 

 mal end is similar, but broader. 



One of the most characteristic bones of Protylopus, and the one which can 

 most readily be distinguished from contemporary genera of similar stature, is 

 the tibia. This is stout and quite long, though less elongate than in the later 

 genera of the series, for it hardly exceeds the skull in length. The proximal 

 end is narrow and the femoral surfaces rather small and placed very obliquely, 

 with a low and bifid spine, which is divided by a broad sulcus ; the cnemial 

 crest is very large and prominent and projects forward as a great keel, but is 

 thinner than in Poebrotherium and does not extend so far down the shaft as in 

 that genus, but its proximal end is thickened and rugose, and it is deeply 

 grooved by the sulcus for the extensor longus digitorum. The shaft, which is 

 almost of uniform breadth throughout, is made trihedral by the cnemial crest, 

 but where that ceases it becomes transversely oval. The distal end is moder- 

 ately expanded and very slightly thickened, giving it, when viewed from below, 

 a rectangular outline ; the malleolus is long and heavy and pointed. The ex- 

 ternal astragalar facet is somewhat the larger of the two, and the intercondylar 

 ridge is prominent, ending dorsally in a conspicuous tongue-like process. No 

 sulci invade the articular surface. The fibular facet is partly external and 

 partly distal, the tibia extending slightly over the distal end of the fibula. 



