136 THE WASATCH AJND BRIDGEB FAUNJE5. 



The species has the linear dimensions of the E. vyomingensis, and differs 

 primarily in the much greater thickness of the bones of the carapace, 

 especially of the vertebral bones. The plastron is thick, but does not so 

 much exceed the corresponding parts of the thicker examples of E. vyoming- 

 ensis. Another character is the great thickness of the costal parts of the 

 axillary and inguinal buttresses. In an antero-posterior diameter they are 

 twice as large as those of E. vyomingensis, but not more prominent trans- 

 versely. The vertebral dermal scuta are a little longer than wide, and the 

 lateral sutures are strongly bracket-shaped, while the anterior and posterior 

 one present an angle forwards on the median line, thus differing from the 

 sutures in E. haydeni. The vertebral bones are longer than wide anterior 

 to the sixth; the latter, with the seventh, are wider. The costal capitula 

 are quite weak. The posterior marginal bones are not recurved, and the 

 anal is not notched, and its border is a little convex. The lateral and ante- 

 rior marginals are not grooved nor recurved at the margin. The dermal 

 grooves of the carapace are generally strong. 



The plastron is of elongate proportions as compared with the ordinary 

 E. vyomingensis. The lip is moderately wide, and has a notch on each side, 

 as in the species just named. The mesosternum is wider than long, and is 

 marked anteriorly by the gular scuta. The humero-pectoral groove reaches 

 but does not cross it posteriorly, in which it differs from that of most of the 

 Bridger species. The smooth border of the anterior lobe of the plastron is 

 very wide anteriorly; that of the posterior lobe is even wider at the posi- 

 tion of the ranges of movement of the thigh, where it is bounded within 

 by a sharp groove. The posterior notch is well marked but open. Tlie 

 dermal sutures are straight and not sinuous, as in E. haydeni. 



Measurements. 



M. 



Length of carapace 380 



Width of carapace at second costal bone 145 



LenRlli of tliird vertebral bone 040 



Width of third vertebral bone 025 



ThickiicHM of third vcrtebrol bone 016 



Length of seveuHi vertebral bono 023 



Width of wventh vertebral bono 033 



Thi('kllf^!w of w^venth vertebral bone OH 



Width of axillary buttress 018 



