1898.] Worti/ian, Extinct Caiiielidce of North America. 107 



The fourth has a well-marked heel and anterior basal cusp, 

 but there is apparently no internal cusp present. The molars 

 are so much worn that their structure is not 

 very apparent. There can be very little 

 doubt however that they had the usual 

 structure. In the heel of the last molar a 

 prominent accessory cusp is seen upon the 

 border of the inner side near the point 

 where it joins the lower posterior inter- 

 nal cusp. In PocbrotJieriuni this cusp is 

 clearly present, but it has fused with the 

 postero-internal, producing a prominent 

 angle at this portion of the crown. In per- 

 fectly unworn teeth of PocbrotheriiDii 7vil- 

 soni, it can be readily demonstrated to be 

 an independent cuspule. 



Of the vertebrae, unfortunately, no cervi- 

 cals are known, consequently it is impossi- 

 ble to say whether they exhibit the peculiar 

 features of the more typical Camelidae or 

 not. The dorsals are well represented in 

 specimen No. 2564, the whole series being 

 present, with the exception of the first 

 three or four, together with all the lumbars 

 locked in jiosition. The vertebrae resemble 

 those of the modern Llamas closely in their 

 general proportions. The bodies of the 

 anterior dorsals are but moderately keeled, 

 and towards the posterior end of the series 

 strongly keeled ; they increase gradually 

 in size from before backward. The neural 

 spine of the fifth is long and recurved, 

 those of the succeeding dorsals decreasing 

 in length posteriorly. The neural spines of 

 the last two are considerably shorter and 

 broader, having an almost vertical direc- 

 tion. The rib facets in the anterior region 

 have their usual relations and positions, the 

 ribs articulating with the vertebrae by two 



