234 



FOSSIL TURTLES OF NORTH AMERICA. 



beds of the same period in the region about Milk River, British America. As the Judith 

 River beds are now known to be much lower in the geological scale than the Laramie it is 

 probable that a distinct species is there included. The Arapahoe and Denver beds being prob- 

 ably above the Laramie, it is not improbable that the remains reported from that horizon by 

 Cope and Marsh belong to a third species of the genus. 



Leidy's type indicated a turtle whose carapace had a length of about 365 mm. The neural, 

 regarded as the fourth, was 26 mm. long and 27 mm. wide. The costal plate believed to be 

 the fifth, was 28 mm. wide at the middle of the length. It is rather strongly archt, showing that 

 the shell was not deprest. This costal had a thickness of 7 mm. where it joined the neurals. 

 It is crost at the proximal end by the costo-vertebral sulcus, from which proceeds the sulcus 

 that separated the third and fourth vertebral scutes. The position of the longitudinal sulcus 

 indicates that the vertebrals had a width of about 65 mm. Leidy's estimate that they were 

 2 inches wide is too small. 



The specimens figured by Cope in his Vertebrata of the Cretaceous Formations of the West, 

 plate vi,figs. 15, 16, were collected in 1873, in northeastern Colorado. No statement is made as 

 to the exact locality, but they probably came from the Denver beds in the region about Bijou 

 Creek. We can not be really certain that they belong to Leidy's species. Cope's fig. 16 

 represents a posterior peripheral, apparently the ninth of the left side, with the sulcus between 

 the third and fourth costals running down its anterior half. The bone is 39 mm. high, 32 mm. 

 wide at the free border, and 9 mm. thick at the costal border. There is no pit for the rib-end. 

 The bone thins to an acute free border. The upper surface is only slightly concave. The 

 sculpture resembles that of the 

 type of the species. A remarkable 

 feature of this bone is the low 

 position of the costo-marginal 

 sulcus. This runs much nearer 

 the free than to the costal border. 



FIGS. 292-295. Compsemyi -victa. 

 Fragments of shell. Xf. 



292. Portion of right costal. No. 6096 



A. M. N. H. 



293. First right peripheral. No. 1085 



A. M. N. H. 



294. Fragment of bridge peripheral. No. 



998 A. M. N. H. 



295. Portion of right hyoplastron. No. 



1015 A.M. N.H. 



In Glyptops plicatulus, as is usual in turtles, it runs nearer the costal border. In the periph- 

 eral here described the scute-covered surface on the inferior side of the bozie extends to within 

 15 mm. of the costal border. The granulation is finer than on the upper side of the bone. 

 The other fragment figured by Cope furnishes little additional information. 



A right eighth costal, No. 6096 of the American Museum of Natural History, collected by 

 Mr. J. C. Isaac, in 1877, in the Laramie beds, on Lance Creek, Wyoming, was at least 40 mm. 

 wide and from 5 mm. to 8 mm. thick (plate 34, fig. 3; text-fig. 292). The proximal portion and 

 a part of the hinder border are broken away. On the lower surface there is the base of a 

 strongly developt rib-head; but there is no ridge corresponding to the rib, nor any projecting 

 distal end of the rib, such as we find in Glyptops. Near the hinder border of the bone is a sulcus, 

 that separating the fourth costal scute from the fifth vertebral. On the peripheral border are 

 two loops of a sulcus, one narrow, the other wider. These appear to have proceeded from the 

 peripheral; but as the peripheral figured by Cope shows the costo-marginal sulci to have run 

 low down on the peripherals, the presence of these loops on the costal is at present inexplicable. 

 Similar irregularly meandering sulci are seen on other bones. The oblique hinder sutural edge 

 of the costal probably articulated with the eleventh peripheral and with the suprapygal. The 

 fourth costal scute may have occupied a portion of the suprapygal, as it does in Kinosternon. 

 In the U. S. National Museum there is a neural, the second or fourth, which was collected by 

 Mr. J. B. Hatcher, on Lance Creek, Wyoming. 



