GLIRES OF THE SANTA CRUZ BEDS. 423 



which are preserved, and two are in contact with the ilia. An isolated 

 caudal from near the end of the tail is more slender and elongate than 

 the corresponding vertebra of Erethizon and indicates a longer and thin- 

 ner tail than in the latter. 



The pelvis is slender in all its parts ; the ilium has an elongate, narrow 

 peduncle, expanding into an anterior plate, which is so crushed that its 

 shape is not determinable, and no ilio-pectineal process is observable. So 

 far as it is preserved, the ischium is laterally compressed and somewhat 

 twisted, and has no distinct sciatic notch. The obturator foramen appears 

 to be of a different shape from that of Erethizon, being narrower dorso- 

 ventrally. 



All the limb bones are very slender and fragile, with large, thin-walled 

 medullary cavity. None of the fore limb bones is complete, but the parts 

 preserved show that they were considerably shorter than those of the hind 

 limb and that the difference was much more marked than in Erethizon. 



The very small and slender humerus has a pronounced deltoid crest, 

 quite like that of Erethizon, but extending somewhat farther distally ; the 

 internal epicondyle is very prominent and is perforated by a minute fora- 

 men which is not present in the modern genus ; the trochlea is low and 

 has no pronounced protuberance for the head of the radius ; the supra- 

 trochlear fossa is quite deep and at one point is perforated, though the 

 anconeal fossa, which in Erethizon is quite deep, is in Sciamys almost ob- 

 solete ; the supinator ridge is large. 



The ulna is extremely slender and has a short olecranon, which, how- 

 ever, is relatively less reduced than in Erethizon, and the facet for the 

 internal part of the humeral trochlea is smaller than in the latter ; the 

 shaft is laterally compressed, becoming very thin toward the distal end, 

 and has a distinct sigmoid curvature. 



The carpus is not known. Of the metacarpus, metacarpals II, III and 

 IV are preserved and these indicate that the manus was probably penta- 

 dactyl. The metacarpals named are not unlike those of Erethizon in 

 shape, but are much shorter and more slender in proportion to the bones 

 of the pes. Metacarpals II and III are of nearly equal length and articu- 

 late on the ulnar side with the magnum and the unciform respectively; 

 IV is considerably shorter. In connection with the latter the phalanges 

 are preserved. Of these the first and second are not especially character- 

 istic, but the ungual is remarkably slender and straight, not very sharply 



