EMYDID^E. 



325 



The seventh peripheral has at its hinder sutural border a thickness of 13 mm. A rather 

 prominent rounded keel runs along on the peripherals over the bridge. 



The broadest vertebral scute is the first. The second and third are of moderate width, with 

 the sides somewhat bracket-shaped. 



The costo-marginal sulci run at a distance of about 2O mm. below the costo-peripheral 

 sutures. On the under side of the nuchal and the first and second peripherals the marginal 

 scutes are 28 mm. wide. 



On the visceral side of that portion of the carapace present (fig. 424) are exhibited the 

 axillary and the inguinal buttresses and the shoulders of bone against which they abut. The 



423- 

 FlGS. 423-425. Echmatemys cyane. Carapace and plastron of type. 



423. Portion of carapace. 



424. Portion of carapace, inner surface, ax. b., axillary buttress; c. p. 6, sixth costal plate; ing.b., 



inguinal buttress. On the left are seen some neurals and the bases of the rib-heads. 



425. Two fragments of the plastron. 



axillary buttress has a maximum width of 25 mm. and is 12 mm. thick. It ascends within the 

 first costal to a point 25 mm. or more'above the upper border of the second peripheral, consider- 

 ably further than the buttress ascends in E. wyomingensts, No. 5987 and No. 5988, A. M. N. H. 

 It abuts against an extremely prominent ridge, 12 mm. thick and 10 mm. elevation above the 

 general surface of the costal. This buttress and ridge are therefore very different from those 

 of the species just mentioned. The distance from the upper end of the buttress to the base of 

 the rib-head is less than the distance from the summit of the buttress to the border of the 

 second peripheral. In E. wyomingensis the former distance is much greater than the latter. 

 The posterior buttress articulates for a moderate distance against the inner surfaces of 

 the fifth and the sixth costals, about as far as in E. ivyomingensis, but it appears that the but- 



