64 The Ottawa Naturalist. [June 



peared in 1876 in the Proceeding-s of the Academy of Natural 

 Sciences of Philadelphia, vol. xxviii, p. 257, as follows : "One of 

 the most abundant, and the larg^est species of the Fort Union 

 beds. The carapace is convex and the plastron flat; the marginal 

 bones are heavy and strong-ly convex on the inferior side. The 

 margin of the plastron is thickened and heavy, characters which 

 also belong to all parts of the carapace. The sutures of the dermal 

 scuta are deeply impressed, and the surtace of the bone is strongly 

 sculptured above and below, and even on the superior face of the 

 thickened margins of the free lobes of the plastron. The sculp- 

 ture consists of round fossae, which are deeply impressed and are 

 arranged quincuncially, so that their borders never form straight 

 lines. The latter are also more or less angulate on the edge, so 

 that the surface has a more than usually rugose character. The 

 typical specimen equals those of the large land tortoises of the 

 Eocene in dimensions." The specimens that Professor Cope had 

 may not have permitted a more detailed definition of the species, 

 but the style of sculpture and other points of resemblance seem to 

 remove beyond doubt the question of the specific identity of the 

 Montana specimens with those from the Old Man and Red Deer 

 rivers. 



The proportions of the component elements of the plastron 

 can be seen by referring to plate III, where a restored outline is 

 given, based on two specimens from the Red Deer River, which 

 are represented in the figure by the dotted portions. The sutures 

 between the bones are shown by the sinuous lines and the bound- 

 aries of the shields by the heavy ones. The dotted lines represent 

 the supposed shape of the end of the posterior lobe, the direction 

 of the sulcus defining the front limit of the femoral shields, and 

 the position of a sulcus that probably crossed the xiphiplastrals, 

 whilst the extent of the hypoplastrals is conjectural. 



The plastron is flat except at the sides where it. bends evenly 

 upward, the lobes are short and broad, and the sternal bridge 

 long. The entoplastral is roughly pentagonal and rather broad. 

 The epiplastrals are of not unusual size and shape, whilst the 

 hyoplastrals are relatively large. A divided intergular shield 

 separates two small gulars, behind which are well-developed 

 humeral shields. The pectorals narrow rapidly toward the sides 



I 



