33 1 



present are a little narrower, as are also the vertebral scutes. The greatest thickness of the 

 nuchal bone is 16 mm. The ninth peripheral is 48 mm. high, 35 mm. wide at the free border 

 and 23 mm. wide at the upper border. Its greatest thickness is 13 mm. This and the other 

 hinder peripherals thin out to an acute border. The pygal is missing but the eleventh periph- 

 erals show that it had a height of 23 mm. and that its right and left sides were convex. The 

 heads of the ribs of these specimens had a diameter of 8 mm. 



The plastron differs in having a slightly narrower anterior lobe, 108 mm., a narrower 

 hinder lobe, n/ mm., and a narrower lip, 41 mm. The entoplastron is 38 mm. long and 

 50 mm. wide. In both specimens the anterior lobe is very short in proportion to its width, 

 being only 67 per cent, thereof. 



The respects in which this species differs from E. cegle are stated under the species just 

 named. E. septaria differs in the expanded anterior lobe, in the greatly thickened epiplastral 

 bones, and in the contracted lip. The acute or subacute anterior border of the carapace of 

 E. ocyrrhoe distinguishes it from E, shaughnessiana. 



E. ocyrrhoe differs from E. hayJeni in having the first vertebral scute much broader in 

 front and rapidly narrowing posteriorly. The other scutes are as broad as long or nearly so; 

 while in E. haydeni they are much longer than broad. E. stevensoniana is a relatively narrower 

 shell, the width being only a little over two-thirds of the length; and more pointed in front and 

 behind. The anterior border of E. stevensoniana is more acute than in E. ocyrrhoe and the 

 suture between the first and second peripherals is 14 mm. thick, instead of 16.5 mm. The 

 epiplastral lips of the two species are different. Comparisons with E. cyane are to be found 

 under the latter species. 



Echmatemys segle sp. nov. 

 Figs. 436-441 . 



Two specimens represent at present this species. These were obtained in the Bridger beds, 

 near Bridger, Wyoming, in 1903. Of these, one, No. 5909 of the American Museum of Natural 

 History, is made the type. The locality where obtained is the western portion of Grizzly Buttes 

 and the level is the lower portion of horizon B. 



The specimen is represented by the complete plastron, the anterior 5 pairs of costal plates, 

 the sixth costal plate of the right side, and a few peripherals. The nuchal bone is missing. 

 An estimate based on the plastron makes it probable that the carapace had a length of 

 330 mm. The surface is smooth, except for some longitudinal striations on the neural bones. 

 The sulci bounding the epidermal scutes are rather deeply and uniformly imprest. The tables 

 below give the dimensions of the neurals and of the vertebral scutes, so far as presented. 



There is little difference as respects 

 width between the proximal and the 

 distal ends of the costal plates. 



The first right peripheral is repre- 

 sented by that portion in front of the 

 costo-marginal sulcus. Its free border 

 is acute at the end next the nuchal bone 

 but rather obtuse at the end next to the 

 second peripheral. The extent of the 

 free border is 38 mm. The greatest 

 height of the second marginal scute was 

 about 29 mm. The greatest thickness 

 of the bone is 12 mm. A part of the right third peripheral is present and will be referred to 

 below. The fifth peripheral is present and shows an angular ridge, along which the upper side 

 of the shell past abruptly into the lower side. This peripheral rises above the ridge mentioned 

 a distance of 35 mm. and it has a width of 40 mm. The seventh peripheral has a length of 

 40 mm. along the free border. Its upper border is broken away. The maximum thickness 

 of the end articulating with the eighth is 13 mm., but it may have suffered some compression. 

 The eighth peripheral measures 33 mm. along the free border and it rises to a height of 45 mm. 

 The vertebral scutes are broad and urn-shaped, quite like those of E. naomi. The table 

 above gives the dimensions. 



