452 Annals of the Carnegie Museum. 



ridges on either side of the median line or keel. The zygapophyses 

 have the usual interlocking features, with evidence of the presence 

 of episphenial processes, although not constant throughout the series. 

 The neural spines have a greater forward slope than those of the 

 recent genera. Posteriorly and near the base the spines send heavy 

 laminae to each postzygapophysis, thus forming a deep triangular pit 

 back of the base of the spines ; a character which is almost entirely 

 absent in the recent camel and the llama. A great similarity between 

 Oxydactylus longipes and the recent forms is noticeable in the trans- 

 verse processes. In the type specimen these are preserved in some 

 instances for more than half their estimated length. The left trans- 

 verse process on the last lumbar is complete and is proportionally 

 flatter than in that of the recent genera, especially the camel, in which 

 the corresponding process is more nearly circular in cross-section. 



TJic Sacrum. — (PL VI, Fig. 8.) There are four firmly coossified 

 centra in the sacrum of Oxydactylus longipes. This region of the ver- 

 tebral column is proportionally somewhat lighter than in the recent 

 forms, as will appear from the comparative measurements. The sa- 

 crum of Oxydactylus longipes is but very little longer, while the great- 

 est lateral expansion is actually less than that of the llama. The first 

 sacral is broad, nearly flat inferiorly, and sends out heavy pleurapoph- 

 yses to meet the ilium, which is supported only by the first sacral 

 vertebra. The neural spines, as in recent forms, are very light, the 

 arches greatly depressed and thin, especially in the first and second 

 sacrals. The last two sacrals have comparatively heavy rounded spines 

 and the centra assume a cylindrical form more like those of the caudal 

 vertebrae. 



The Caudals. — In skeleton No. 562 there is preserved only a single 

 fragment of a median caudal. Judging from the rapid tapering of the 

 centra in the sacrum the tail was not longer than that of the camel, or 

 may even have been shorter. 



Tlie Ribs. ^— There are in the type (No. 918) a number of rib frag- 

 ments, including the first rib on one side nearly complete. The gen- 

 eral form of the ribs resembles that of the recent species. The first rib 

 is short, subcylindrical proximally, and considerably more flattened 

 and expanded distally. The fragmentary remains of the ribs indicate 

 that they were broad and rather thin in the anterior half of the thorax, 

 while they become more rod-like posteriorly. The short distance be- 

 tween the head and the tubercles of the ribs would seem to indicate a 

 rather small thorax. No sternal bones are known. 



