3 28 



FOSSIL TURTLES OF NORTH AMERICA. 



he regarded the bones of the carapace, especially the neurals, as much thicker than those of the 

 species just mentioned. It is doubtful if this is a correct statement. His statement that the 

 axillary buttresses are thicker than those of E. wyomingensis appears to be true. The capitula 

 of the ribs are fully as broad as those of E. haydeni, altho apparently not so thick. The periph- 

 erals are about as much recurved as those of E. wyomingensis. 



The following appear to be characters distinguishing this species from E. wyomingensis: 

 The axillary buttresses, and apparently also the inguinal, are thicker; the humero-pectoral 

 suture passes behind the entoplastron; the femoral scute extends inward on the upper surface 

 of the hinder lobe of the plastron as far as the inner border of the inguinal buttress; the 

 anterior border of the carapace has a much more obtuse edge; the free border of the epiplastron 

 is thicker and more obtuse; and the smooth band on the upper surface of the hinder lobe is 

 much wider, as is also the thickening on the upper side of the epiplastral lip. 



From the type of E. shaughnessiana there are missing the nuchal bone, except a fragment; 

 the eighth neural; both suprapygals; all the peripherals over both bridges, except a part of the 

 right fourth; some of the free peripherals of the left side and the seventh of the right side; 

 the distal ends of two left costals; the left half of the plastral lip; and parts of the bridge. 

 The forms of the nuchal, the eighth neural, and the suprapygals and pygal can be quite accur- 

 ately determined from the surrounding bones, so that from one side or the other of the shell we 

 have the means of determining nearly all the elements. 



The total length of the carapace (plate 50, fig. i ; text-fig. 428), in a straight line, is 352 

 mm. Cope's measurement of 380 mm. includes the curve. The width was approximately 270 

 mm. Near the midline in front the outline has been gently concave; the posterior margin has 

 been broad and rounded. 



The table herewith presents the dimensions of the nuchal, neurals, and suprapygals. 

 The third neural has a thickness of 15 mm.; the third costal at its outer end is 7 mm. thick. 



The costals show no remarkable peculiarities. The second 

 is only 28 mm. wide at its proximal end; 46 mm. at its distal 

 end and 8 mm. thick near the border of the vertebral scute. 

 The fifth and sixth of the left side are, as an individual pecu- 

 liarity, co-ossified proximally and measure together only 47 

 mm.; whereas the corresponding ones of the other side are 

 distinct from each other and measure 59 mm. The periph- 

 erals resemble those of E. wyomingensis, but the anterior 

 are higher and far less acute. The posterior are acute. 

 However, they are not gradually thinned out, as are those 

 of E. wyomingensis, but come rather abruptly to an edge. 

 Cope's figure (Tert. Vert., plate xxiii, fig. 6) represents this 

 condition only moderately well. The first peripheral is 12.5 

 mm. thick where it joins the nuchal. The second is 45 mm. 

 high; its free border is 37 mm. long. The third is 50 mm. high and 44 mm. along the free 

 border. On these the marginals ascend about 24 mm. above the free border of the bones. 

 Cope's figure of the carapace represents the seventh right peripheral as present; but it is 

 not now in the collection. The corresponding one of the left side is present. 



The width of the first costal bone is 60 per cent, of the length along the hinder border. 

 The scutes of the carapace are rather broad and their lateral sulci are bracket-shaped. The 

 nuchal is missing. The table below gives the dimensions of the vertebral scutes. 

 The upper borders of the marginal scutes run consid- 

 erably below the sutures between the costal and peripheral 

 bones. All the scutal sulci are narrow, but sharply 

 imprest. 



The plastron (plate 50, fig. 2; text-fig. 429) has a total 

 length of 342 mm., falling short of the length of the cara- 

 pace only 10 mm. In the midline the length is 13 mm. 

 less, on account of the notch. The anterior lobe is 97 

 mm. long and, at the base, is 144 mm. wide. The lip, as 

 seen from below, and measured from one gular suture to 



Width. 



7* 



26 



24 

 29 

 28 



70 



Dimensions of vertebrals. 



