324 



FOSSIL TURTLES OF NORTH AMERICA. 



The gular scutes are 41 mm. long; the humerals, 25 mm.; the pectorals, 55 mm.; the 

 abdominals, 70 mm.; and the femorals, 47 mm. 



The axillary scute extends backward in a long point to come into bare contact with the 

 fifth marginal. The inguinal scute extends torward and joins narrowly the sixth marginal. 



This species differs from E. naomi 

 in the form of the vertebral scutes, in 

 the lack of grooves for the sulci of the 

 carapace, in the very different form of 

 the front of the anterior lobe, and in 

 the axillary and inguinal scutes. The 

 broad neurals, the very broad fifth ver- 

 tebral scute, and the plastral lip differ- 

 entiate it from E. stevensoniana. The 

 acute anterior border of the carapace, 

 the plastral lip, and the advanct posi- 

 tion of the humero-pectoral sulcus sep- 

 arate it from E. shaughnessiana. The 

 very different plastral lip, among other 

 characters, removes it from E.septaria. 

 E. ocyrrhoe has the costal plates dif- 

 ferentiated so that the ends are alter- 

 nately wider and narrower; the epi- 

 plastral lip is different from that of E. 

 arethusa; as are also the axillary and 

 inguinal scutes. E. tfgle has the verte- 

 bral scutes urn-shaped, the anterior 

 lobe is very different, and the axillary 

 and inguinal scutes fall short respect- 

 ively of the fifth and sixth marginals. 

 The plastral lip of E. cyane is widely different; the axillary scute falls short of the fifth 

 marginal; the inguinal far short of the sixth; the second and third peripherals measure 

 together 64 mm. along the free border, while the same bones in the type of E. arethusa measure 

 85 mm. E. haydeni, so far as known, differs in having the fourth neural octagonal, the verte- 

 bral scutes narrower, and a very different form of epiplastral lip. 



Figs. 421 and 422. Echmatemys arethusa. Anterior 



lobe of plastron. 



421. Lower surface. 



No. 5920 A. M.N. H. 



422. L T pper surface 



Echmatemys cyane sp. nov. 

 Figs. 4 2 3-4*7- 



No. 5924 of the American Museum of Natural History is a fragmentary specimen present- 

 ing most ot the left side of the carapace, including four neurals, most ot the left side of the 

 plastron, and a part of the right side. The specimen was secured by the expedition in 1903, 

 into the Bridger Eocene, at Grizzly Buttes, Wyoming. Its horizon is therefore that called B. 

 The length of the carapace (fig. 423) of this individual can not be exactly determined. 

 From the front of the nuchal to the hinder end of the sixth neural is 246 mm., from which fact 



it is estimated that the carapace had a length of 340 mm. Like 

 most of the Bridger species of the genus, this species had a thick 

 shell. The surface of the carapace is mostly smooth. 



Of the nuchal only a portion of the left side is present, but 

 this shows that its width in front was very close to 50 mm. The 

 greatest thickness is 15 mm. The first neural is not present. 

 Those preserved show the dimensions given in the table here- 

 with. These neurals have a thickness of 12 mm. The costals 

 have the two ends of each about the same width. The width of 

 the first costal equals jj per cent, of its height. 



The dimensions of some peripherals and of some vertebral and marginal scutes are given 

 in the table on the following page. The third peripheral is half as high as the first costal. 



