226 FOSSIL TURTLES OF NORTH AMERICA. 



KEY TO THE AMERICAN GENERA OF FOSSIL DERMATEMYDIDJE. 



A. Upper Cretaceous genera. 



a 1 . No inframarginals, coarsely sculptured with pits, furrows and pyramidal elevations Basilemys 



a 2 . Sculpture fine and granular Compsemys 



a 3 . Sculpture consisting of shallow pits. Borders of carapace acute-edged. Plastron 

 rounded in front and behind, with full set of plastral scutes. Hinder marginal 



scutes rising well on the costal bones Adocus 



a*. Like Adocus, but with axillary and inguinal buttresses and costals sending long 



rib-heads into the peripherals. Bones thin Zygoramma 



a b . Shell thick and heavy ; the free borders of carapace thick and obtuse. Hinder 



marginal scutes rising little or not at all on the costal bones Agomphus 



a 6 . Vertebral scutes said to be usually narrower than the neural bones Homorophus 



AA. Tertiary genera. 



a 1 . Like Adocus, but hinder marginal scutes not rising on costal bones. Torrtjon.. . Alamosemys 



a 2 . See A. a 5 above. Hinder lobe of plastron pointed. Midway Agomphus 



a 3 . Shell thick; free borders acute; three ridges along back; the plastron rather loosely 



joined to carapace. No inguinal buttresses. Torrejon Hoplochelys 



a*. Like Hoplochelys, but without inguinal buttresses. Wasatch Kalltstira 



a 5 . Not well known. At least the anterior peripherals obtuse. Wasatch Notomorpha 



a 6 . A full set of neurals. Carapace smooth, with a median carina on rear of cara- 

 pace. Plastron sutured to carapace. Wasatch, Wind River, and Bridger. . . . Baptemys 

 a 1 . Shell finely sculptured. Plastron much reduced and loosely joined to the carapace. 



Bridger Anosteira 



a 8 . Shell smooth; no buttresses; five pairs plastral scutes. Oligocene Xenochelys 



Genus BASILEMYS Hay. 



Shell highly sculptured. Epiplastra much thickened. Bridge wide. Intergular scutes 

 present. Pectorals greatly expanded at the midline, narrowed laterally. An axillary and an 

 inguinal scute but no other inframarginals. 



Type: Compsemys vanolosus Cope. 



This genus differs from other known genera of Dermatemydidae in having no infra- 

 marginals, except the axillary and the inguinal. 



Basilemys variolosa (Cope). 

 Plate 32, fig. 4; plate 34, fig. i; text-fig. 287. 



?Compsemys ogmius, COPE, Vert. Cret. Form. West, 1875, pp. 91, 261; Proc. Acad. Nat. Sci. Phila. 



1875, p. 9; Brit. N. A. Bound. Surv., Report on Geol. and Resources 1875, p. 336. 

 Compsemys variolosus, COPE, Proc. Acad. Nat. Sci. Phila. 1876, p. 257; Bull. U. S. Geol. Surv. Terrs., 



in, 1877, p. 573. 

 Adocus variolosus, LAMBE, Ottawa Naturalist, xv, 1901, p. 63, plates iii-vi; Cont. Canad. Palaeont., 



II (410), p. 39, plate ii, text-figs. 4-6. 



Basilemys variolosus, HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 445. 

 Adocus (Basilemys) variolosus, OsBORN, Cont. Canad. Palaeont., Ill (4*), 1902, pp. 12, 16. 

 Basilemys ogmius, HATCHER, Bull. U. S. Geol. Surv. No. 257, 1905, p. 76. 



The type of the present species consists of nearly the whole of the plastron, various periph- 

 eral bones, and two imperfect costal plates. These are now in the American Museum of 

 Natural History, and bear the catalog number 1465. This type, with fragments of other 

 individuals, was collected for Professor Cope, in 1876, by Mr. Charles H. Sternberg, in the 

 Judith River beds of Montana. Since that time other specimens of the species have been 

 collected by members of the Geological Survey of Canada, in Judith River deposits, just 

 north of the United States boundary line and east of the Rocky Mountain range. More 

 accurately, the remains were taken on Mackay Creek, along Old Man River, and on Red 

 Deer River. 



Fig. 287 is reproduced mostly from Cope's type, but it is probable that the fragment of 

 bone around the axillary notch and the piece of epiplastron do not belong to the same indi- 

 vidual as the remainder of the specimen, these anterior pieces being somewhat larger than we 



