622 Troxell — Vertebrate Fossils of Rook Creek, Texas. 



direction of the median plane, or else is simply an old age 

 character. 



Very little is known of the fossil ancestors of E. asinus. 

 According to Flower and Lydekker (5.383), teeth and bones 

 from the Pleistocene deposits in Madras are considered to be of 

 that species. Specimens related to the ass and quagga have been 

 reported from America, but the resemblance is based on seem- 

 ingly meager evidence. Nearly every part of the skeleton of 

 E. calobatus which is known, however, shows a closer relation 

 to E. asinus than to either E. caballus or E. scotti. 



Fig. 6. 



Camelida?-. 



From quarry number one camel material was found, consist- 

 ing of fragments and small bones. By the method of ratios, 



comparison was made with a recent 

 form, and from the relative size it was 

 found that there were three different 

 individuals, probably representing as 

 many species. 



Auchenia hesterna. — The parts 

 which were larger than the standard 

 Camelus bactrianus No. 1551 of Pea- 

 body Museum showed very definite 

 characters which undoubtedly correlate 

 the specimen with the South American 

 llama. The morphology of the larger 

 bones as well as the constancy of ratio 

 to the llama emphasizes this close rela- 

 tion, although the fossil is two or two 

 and one-half times as large as the 

 recent South American form. 

 The large third upper molar (fig. 6) when compared to the 

 standard gave a ratio considerably over 100 per cent, identify- 

 ing it as belonging to the largest animal. This large tooth, 

 with its broad grinding surface, cement-iilled lakes, and hypso- 

 dont crown, indicates the grazing habit of its owner. Because 

 of this and because of the good cursorial adaptation, as shown 

 by the high speed index of the limb bones (fig. 7), the animal 

 is judged to have been a plains dweller in a semi-arid climate, 

 traveling far for food and water. 



Eschatius conidens. — There were found parts of the skeleton 

 of a camel of moderate size, giving an average ratio less than 

 90 per cent that of the standard. With this group was a 

 fragment of the maxillaiw (fig. 8) containing two molar teeth, 

 whose average ratio is 84 per cent. Especial interest is attached 

 to this portion of skull because it shows, in front of the first 

 molar, a small round alveolus representing a conical tooth, the 



Fig. 6. Auclienia hes- 

 terna, third upper molar. 

 1, crown, and 2, side 

 vieAvs. One-third nat. size. 



