3 68 



FOSSIL TURTLES OF NORTH AMERICA. 



This formation is placed by Lapparent at the base of the Oligocene. The specimen is a very 

 imperfect one, and it may be said that the genus is only approximately determinable. Dr. 

 A. E. Andrews (Surv. Dept., Pub. Works Ministry, Geol. Surv. Egypt, 1903; Catalogue Tert. 

 Vert. Fayum, Egypt, 1906, p. 278, plate xxiv) has described a land-tortoise from the Upper 

 Eocene of Egypt to which he has given the name Testudo arnrnon. If a true Testudo, it is the 

 oldest known. The publisht figures show that the neurals are variable in form, but the relation- 

 ships to typical Testudo are so close that it may be accepted as belonging to this genus. In 

 some respects it appears to be intermediate between Testudo and Hadrianus. 



The oldest known representative of the family is Hadrianus majusculus, of the Wasatch 

 beds of New Mexico. 



The following table presents a list of the North American fossil species belonging to the 

 Testudimdae so arranged as to exhibit their geological sequence: 



Pleistocene. 

 Pliocene. 



Miocene. 



Oligocene. 



Eocene. 



Species. 



Equus, or 

 Sheridan beds 



Peace Creek. 



Blanco. 



Loup Fork. 



Testudo hexagonata, T. laticaudata, T. atascoss (Texas). 



Testudo crassiscutata (Florida). 



Testudo pertenuis, T. turgida, T. carnpester (Texas). 



Testudo klettiana, T. undata (New Mexico); T. niobrariensis, T. hollandi, T. ede 

 (Nebraska): T. impensa (Montana); T. gilberti, T. orthopygia (Kansas); T. 

 arenivaga (Nebraska). 



Deep River 



and 

 Pawnee Creek. 



John Day. 



White River. 



Unita. 



Testudo pansa, T. osborniana (Colorado); T. arenivaga (Nebraska); T. erniliae (South 



Dakota). 

 Testudo vaga (Wyoming); ?T. peragrans, T. farri, T. inusitata (Montana). 



Jackson. 

 Bridger. 



Wasatch. 



Puerco. 



Stylemys conspecta, S. capax (Oregon); S. calaverensis (California). 



Testudo brontops, T. thoinsoni (South Dakota); ?T. peragrans (Montana); T.ligonia, 

 T. cultrata, T. laticunea, T. amphithorax, T. quadrata (Colorado); T. exornata 

 (Assiniboia); Stylemys nebrascensis (South Dakota, North Dakota, Nebraska, 

 Wyoming). 



Hadrianus tumidus (Utah). 



Hadrianus schucherti (Mississippi). 



Hadrianus corsoni (Wyoming); Achilemys allabiata (Wyoming). 



Hadrianus majusculus (New Mexico); H. corsoni ? (New Mexico). 



We can not doubt that the predecessors of Hadrianus will yet be found in the Puerco beds 

 or their equivalents. We may even look confidently for more primitively constructed Tes- 

 tudinida? in some of the Upper Cretaceous deposits. They are more likely to occur in river 

 valley formations or aeolian accumulations. 



Considering the large size of Testudo brontops, the grade of its differentiations, and the 

 great number of species of Testudo which made their appearance in the Oreodon beds of the 

 Oligocene we may be sure that species of the genus will yet be discovered in some of the upper 

 formations of the Eocene of America; as they have already been found in the Upper Eocene 

 of northern Africa. 



Nevertheless, it seems to the writer that the family was, in the earlier half of the Eocene, 

 in a stage of development represented by Hadrianus corsoni of the Bridger, and that Testudo 

 brontops, with its only slightly differentiated costal plates, represents a stage which existed 

 possibly even in the Upper Eocene. It may be concluded therefore that any members of the 

 family that shall be found in the Puerco and Upper Cretaceous will display further approxi- 

 mations to the Emydidae. 



It will be interesting to consider in the light of knowledge derived from both the living and 

 the fossil species of the family the special characters which they have developt since their first 

 appearance: as we might say, the goal toward which they have been striving. 



With regard to the shell we see that it is usually very high and convex. There are various 

 exceptions to this statement; nevertheless, we find no species so deprest as some of the Emy- 

 didae; and the height and convexity will average much higher than among the species of the 



