IOO FOSSIL TURTLES OF NORTH AMERICA. 



The piece of epiplastron present is 9 mm. thick. The gulo-humeral sulcus crosses the 

 hinder end as in Glyptops and Baena. 



The length of the hyoplastron, from the epiplastral suture to the mesoplastron, is 120 mm. 

 The width of the anterior lobe was about 142 mm. The distance from the axillary notch to 

 the mesoplastron measured very close to 50 mm. The thickness of the bone at the entoplastral 

 suture is 6 mm. The free border in front of the axillary notch is subacute. Most of the border 

 which rose to meet the peripherals is broken away. A portion of the sulcus between the 

 abdominal scute and the anterior inframarginal is present. 



The length of the hypoplastral at the midline is 90 mm.; the width at the base of the 

 hinder lobe, 80 mm.; the width from the midline to the union with the bridge peripherals, 

 130 mm. A portion of the outer end of the bone is missing, but a section of the sulcus is seen 

 starting forward from the inguinal notch and section of another sulcus between the hinder 

 inframarginal and the contiguous marginals. The hinder inframarginal has a width of about 

 45 mm. Its anterior end appears to have extended on the mesoplastron. 



The fragment of xiphiplastral is 53 mm. long. It shows the free border. This is subacute, 

 and from it the bone thickens soon to 10 mm. No portion of the upper surface was covered 

 with scutes. On the lower surface the femoro-anal sulcus crost the bone about 30 mm. behind 

 the suture with the hypoplastron. The form of the hinder border of the lobe can not be 

 determined. 



Of the skull there is present the pedicel of the left quadrate. The condyle for the lower 

 jaw is concave, 1 1 mm. from side to side, and less than 5 mm. antero-posteriorly. At the inner 

 side of this condyle there ascends toward the lower end of the parietal plate a sharp ridge. The 

 rough surface for the pterygoid lacks 8 mm. of reaching the condyle, a fact that shows that 

 this genus did not belong to the Pleurodira. 



The upper surface of the carapace was more or less uneven, especially along the midline. 

 All the articular borders of the bones are striated perpendicularly to the sutures. Besides this, 

 there is a delicate pitting of the surface which gives the effect of leather. The lower halves 

 of the costals are markt by coarse ridges, which have been produced during the growth of the 

 costal scutes. 



The plastral bones have all the sutures conspicuously markt by striae, which run at right 

 angles with the sutures. The whole surface is occupied by a fine network of delicate lines. 



Genus POLYTHORAX Cope. 



An insufficiently known genus of uncertain position. Plastron suturally united with the 

 carapace; furnisht with the usual scutes, besides intergulars and interhumerals. Lower jaw 

 with narrow ramus; the triturating surface bounded outwardly by a sharp margin; the 

 symphysis short. 



Type: Polytharax mtssunensis Cope. 



This genus is arranged provisionally among the Baenidae; but it is probable that it and 

 Arch&ochelys Lydekker belong to a distinct family. 



Polythorax missuriensis Cope. 



Polythorax missuriensis, COPE, Proc. Acad. Nat. Sci. Phila. 1876, p. 258; Bull. U. S. Geol. and Geog. 

 Surv. Terrs., in, 1877, p. 573. HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 438. HATCHER, 

 Bull. U. S. Geol. Surv. 257, 1905, p. 77. 



It is not at present known what has become of the type of this species. It was found in the 

 Judith River deposits of Montana, in 1876. The plastron appears to have been pretty complete, 

 but we are not told how much of the carapace was secured. No part of the species has ever 

 been figured. 



The plastron had a total length of 183 mm.; hence the individual was not a large one, 

 perhaps attaining about the size of our Trachemys elegans. The anterior lobe had a length of 

 49 mm. The bridge was 76 mm. wide and as long. The anterior lobe is stated to have been 

 narrower at the base than the bridge. We must conclude therefore that this lobe was not one- 

 third as wide as the carapace. Its anterior extremity was rounded. The width of the base of 



