39 



FOSSIL TURTLES OF NORTH AMERICA. 



A 2 . Lower Miocene species: 



g. Lip prominent, twice as wide as long, and nearly as thick as long pi-ragrans 



10. Pygal convex up and down on upper side aremvaga 



n. Lip not greatly projecting; pectoral scutes nearly half as wide on midline as 



abdominals vaga 



12. No 4-sided or X-sulrcl murals; pectoral scutes about one-fifth as wide as abdom- 

 inals emiliee 



A 3 . Deep River and Pawnee Creek (Middle Miocene) species: 



I J. Lip not projecting far; pectorals only one-seventh the width of the abdominals . jam 



14. Neurals as in T. emilite; the gulars reaching the entoplastron inusitata 



15. Shell broad and deprest; lip tapering; pectorals about one-third the abdominals . pansa 



16. Shell vaulted; pectorals one-twenty-fifth the abdominals, or less osborntana 



/'. Loup Fork: 



17. Lip abruptly projecting; pectorals one-eighteenth the width ot the abdominals unpensa 



18. Hinder peripherals and pygal with free border flared upward; pygal narrowing 



toward the free border undata 



it), l'ygal plane; its sides parallel klettiana 



20. Lip rounded, little projecting; resembles vngtt of the Lower Miocene mobrarensis 



21. Strongly projecting lip; pectorals about one-eleventh the width of abdominals. . orthopvgta 



22. Skull only; consult figures gilberti 



23. First and third neurals 4-sided; second and fourth octagonal; lip prominent; 



pectorals about one-fifth the width of abdominals ed<z 



24. First, third, and fifth neurals 4-sided; second and fourth octagonal; lip moderately 



prominent; pectorals one-fourth the width of abdominals hollandi 



A". Pliocene species: 



25. Lip prominent; all the sulci deeply sunken and wide; free borders of the peripherals 



deeply nocht by the sulci turgida 



26. Shell broad and deprest; the vertebral scutes wider than long; shell thin pertenuis 



27. Lip prominent; truncated; pectoral scutes nearly half as wide as the abdominals . . campester 



28. Hinder peripherals thick and with very obtuse free border obtusn 



29. Anterior lobe of plastron rapidly tapering forward; borders of lip continued in 



same lines; bones thick and heavy crassiscutatu 



A h . Pleistocene species: 



30. Lip about four-fifths as long as wide, thick behind; notch in rear of plastron four 



times as wide as deep laticaudata 



31. Lip rounded; notch in rear not three times as wide as deep; borders of hinder 



lobe rapidly converging backward hexagonata 



52. Lip rounded but prominent; borders of hinder lobe slowly converging atascoste 



Testudo brontops Marsh. 



Plate 65, figs. 1, 2; text-figs. 504, 505. 



T , itudo brontops, Marsh, Amer. Jour. Sci. (3), XL, 1890, p. 179, plate viii; Vert. Foss. Denver Basin, 

 in Mon. U. S. Geol. Surv., xxvn, 1897, pp. 523, 527, figs. 95, 96. Dana, Manual Geol., 1896, 

 p. 901, fig. 1516. Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 451; Amer. Jour. Sci., (4) 

 win, 1904, p. 272, figs. 6, 7. 



The type of this species is a fine large shell which was collected tor Prof. O. C. Marsh, in 

 the year 1888, by Mr. J. B. Hatcher, and is now in the Peabody Museum, at Yale University. 

 It was obtained in the Titanotherium beds of Indian Creek, in the southeastern corner of 

 Pennington County, South Dakota. No considerable parts of the shell are missing and it has 

 been only slightly crusht. The specimen bears the record " Box 27, 1985." 



In form this magnificent tortoise was broad and probably ot only moderate height. The 

 front of the carapace (plate 65, fig. I ; text-fig. 504) is somewhat concave in outline, the lateral 

 angles bmad, rounded and flaring upward. The sides were nearly perpendicular. The hinder 

 border is broadly rounded, with the peripherals over the limbs considerably flaring and with 

 the pygal incurved toward its free border. Where the sulci cross the free borders of the periph- 

 erals the latter are somewhat notcht; and where they cross the borders of the carapace above 

 the bridges they lie in grooves so deep that the interspaces appear to be strongly swollen. The 

 free borders of all the peripherals come down to an acute edge. The length ot the carapace 

 is 71 1 mm.; the greatest width is 651 mm. 



