326 



FOSSIL TURTLES OF NORTH AMERICA. 



tress of the latter did not project so far from the inner surface of the carapace and was thinner. 

 In E. wyomingensis, as represented by No. 5987, at a point 20 mm. below its summit, the but- 

 tress projects inward from its articulation only 9 mm.; in E. cyane it projects inward 23 mm., 

 a difference hardly to be regarded as merely individual. 



The plastron (fig. 425) had a length very close to 325 mm. On account of the absence of 

 some fragments which connected parts which are present, the exact length can not be deter- 

 mined. The length of the anterior lobe 

 was very close to 90 mm.; the width was 

 not far from 130 mm. The epiplastral 

 lip has a width of 54 mm. It projects 

 but slightly beyond the general outline 

 ofthelobe. It is truncated, with an acute 

 free border. The lateral portion con- 

 sists of a stout tooth separated from the 

 remainder of the lip by a deep slit. On 

 the upper side the thickening of the 

 epiplastrals (fig. 426) extends backward 

 from the free border a distance of 28 

 mm. The epiplastrals are nowhere great- 

 ly thickened, the maximum being 1 1 mm. 

 The entoplastron had a length close to 

 49 mm., and the width has been 56 mm. 

 It is rounded in front and behind. 



The bridge has a width of 132 mm. 

 The plastral bones are 21 mm. thick at 



416. Upper surface of epiplastral lip. 



427. Upper surface of left side of hinder lobe. 



FIGS. 426 AND 427. Echmatemys cyane. Plastron 

 of type. X i- 



the crossing of the median longitudinal 

 and the hyohypoplastral sutures. 



The hinder lobe has a length of 1 13 mm. The width appears to have been about 146 mm. 

 The beveled surfaces on the upper side of the lobe (fig. 427) have a width of 28 mm. at the 

 hypoxiphiplastral sutures, of which width 21 mm. were covered with horny scutes. The thick- 

 ness of the bones at the sutures just mentioned is 12 mm. 



The inguinal buttresses send their bases inward from the free borders of the posterior lobe 

 a distance of about 33 mm., almost half the distance to the midline. Thus they extend 

 inward further than in E. wyomingensis, but not so far as in some other species of the genus. 



The gulars have a length of 57 mm.; the humerals, about 55 mm.; the pectorals, 55 mm.; 

 the abdominals, 90 mm.; the femorals, about 55 mm.; the anals, about 42 mm., all measured 

 at the midline. No part of the axillary scute is seen, but it failed by at least 28 mm. of reaching 

 the fifth marginal. It could have joined the anterior end of the fourth for only about 10 mm. 

 The inguinal scute lacks 10 mm. of reaching forward to the sixth marginal. 



It is hardly necessary to compare at length this species with E. shaughnessiana, which has 

 a thick epiplastral lip and a thick rounded free border on the nuchal; or with E. (egle, with 

 its urn-shaped vertebral scutes; or with E. arethusa, with its contracted epiplastral lip; or 

 with E. naomi, with its urn-shaped vertebral scutes and sulci lodged in deep grooves. 



From E. wyomingensis it differs in having the inguinal buttresses reaching inward about 

 half-way to the midline, in having the axillary buttresses ascending nearer the neurals, in 

 having the epiplastrals thickened farther backward on the upper side of the symphysis and in 

 having wider vertebral scutes. E. ocyrrhoe differs in having the vertebral scutes, especially the 

 second, considerably wider and in having the marginal scutes of the anterior half of the shell 

 rise higher on the peripherals. The American Museum specimen of E. stevensontana has 

 almost exactly the size of that of the present species, so that comparisons may be readily 

 made. E. stevensoniana has narrower neurals and narrower vertebral scutes. The plastron of 

 E. stevensoniana appears to be thicker than that of E. cyane. Measured behind the abdomino- 

 femoral sulcus and one-third the distance from the midline to the free border, plastron of the 

 former is 8.3 mm. thick; of the latter II mm. The axillary scutes of E. stevensoniana extend 

 backward to the fifth marginal, while in E. cyane they fall far short of the latter marginal. In 



