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17 



WHITE RIVER SELENODONTS 



free from the radius, which has a broad, antero-posteriorly compressed and 

 oval shaft. The carpus is quite traguline in appearance, the magnum being 

 so shifted as to have only a lateral contact with the lunar ; it is also coossified 

 with the trapezoid, which is" very unusual in this group. The manus contains 

 four complete digits, though the lateral metacarpals (mc. ii. and v.) are exceed- 

 ingly slender. No anterior cannon-bone is formed. 



The hind-limb greatly exceeds the fore-limb in length and stoutness. 

 The pelvis is like that of Poebrotherium and altogether different from that of 

 the tragulines in shape, and much the same statement applies to the femur, 

 though the distal end of this bone is remarkable for the narrowness and length 

 of its rotular trochlea. The proximal end of the fibula is a short spine 

 anchylosed with the tibia ; the shaft is wanting, and the distal end is a malle- 

 olar nodule, wedged in between the tibia and the calcaneum. The navicular 

 and cuboid are coossified, which, like the union of the trapezoid and magnum, 

 is very rare in this group of selenodonts. A cannon-bone is formed by the 

 coossification of the median metatarsals (mt. iii. and iv.), to which are attached 

 the splint-like proximal ends of the lateral pair (mt. ii., v.). The distal end of 

 the cannon-bone (Plate I., fig. 2) in uninjured specimens is quite deeply cleft, 

 and shows in a slight but unmistakable way the eversion of the metatarsal 

 trochlea; which is so characteristic of the Tylopoda ; the carina is confined to 

 the palmar aspect of the trochlea;. The phalanges are like those of Poe- 

 brotherium, and the unguals are elongate, slender, and pointed. 



That the whole appearance of the skeleton of Leptomeryx and many 

 details of its structure closely resemble those of the tragulines is not to be 

 denied, and I formerly referred it to that group with much confidence ('gic, p. 

 360), in this following Cope's example ('89, p. 121). The new material just 

 described has convinced me, however, that this reference is erroneous, and that 

 Rutimeyer was right in regarding it as essentially tylopodan ('83, p. 98), a con- 

 clusion which Wortman has also reached in his latest paper ('98, p. 100). 



Hypertragulus Cope. 

 Plate I., Figures 3, 4. 



This genus is a remarkable variant of the Leptomeryx type, to which it is 

 obviously allied, though departing less from the main tylopodan stem, as rep- 

 resented in Poebrotherhim and the John Day Gompliotherhim. 



The dental formula is : 1^, Cy, P^, M-|. From the material at present 



