Troxell — Vertebrate Fossils of Rock Creeks Texas. 637 



Two distinct types of camel were found. The large 

 Aucltenia hesterna, showing characters closely relating it to 

 the South American species, is a plains or desert form, as 

 indicated by its grazing and cursorial adaptations. Eschatius 

 conidens is of moderate size. This genus is characterized by 

 the loss of all the premolars but one, which is a simple cone. 

 The teeth indicate the browsing habit of this animal, while the 

 associated limb bones are probably those of an agile form, 

 adapted to hilly country. 



By "ratios' 1 the canid material was easily separated into 

 four distinct groups, which were judged to represent as many 

 different species. The largest is Canis dirus, which Professor 

 Cope had already found at Rock Creek. The second animal is 

 designated C. texanus, n. sp., cf. ?nississippie?isis. Of the 

 latter only two limb bones are known, while the new species 

 is based on the left ramus with all its teeth, and on five parts 

 of the skeleton. The third group consists of but a single upper 

 molar. The fourth group comprises two bones which by 

 reason of their small size were identified as C. temerarius. 



A tusk and a fragment of the ramus of Platygonus com- 

 pressus was discovered. Parts of three or more individuals of 

 the tribe of giant sloths were found. These, with P. com- 

 pressus, indicate the early Pleistocene age of the fauna. 



The identification of the elephant material is doubtful, but 

 because of its association and small size, it is judged to be a 

 young imperial mammoth. 



The extinction of this entire fauna, except the dogs and 

 turtles, was probably brought about in a more or less direct way 

 by the advance of the early Pleistocene glaciers, causing a 

 change in the environment and rendering it uninhabitable. 



Bibliography. 



1. Allen, J. A., 1876. This Journal (8). vol. xi, pp. 47-57. 



2. Cope, E. D., 1884. Proc. Amer. Phil. Soc. vol. xxii, pp. 1-27. 



3. Cope, E. D., 1895. Jour. Acad. Nat. Sci. Phila. (2), vol. ix, pp. 

 453-459. 



4. Cope, E. D., 1899. Idem, vol. xi, pp. 193-267. 



5. Flower, W. H., and Lydekker, E., 1891. An Introduction to the 

 Study of Mammalia Living and Extinct. London. 



6. v Gidley, J. W., 1900. Bull. Amer. Mus. Nat. Hist., vol. xiii, pp. 

 111-116. 



7. Leidy, Joseph, 1854. Proc. Acad. Nat. Sci. Phila.. vol. vii, pp. 

 199-201. 



8. Leidy, Joseph, 1856. Jour. Acad. Nat. Sci. Phila. (2), vol. iii, pp. 

 166-171. 



9. Leidy, Joseph, 1858. Proc. Acad. Nat. Sci. Phila., vol. x. pp. 20-29. 



10. Leidy, Joseph. 1869. Jour. Acad. Nat, Sci. Phila. (2), vii, pp. 1-472. 



11. Leidy, Joseph. 1873. TJ. S. Geol. Surv. Terr., Fiist Ann. Rept., pp. 

 14-358. 



12. Merriam, J. C. 1903. Univ. Calif. Pub., Bull. Dept. Geol., vol. iii, 

 pp. 277-290. 



