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PROCEEDINOS OF THE NATIONAL MUSEUM. 



VOL. 56. 



shell. The first and second peripherals are relatively thin with acute 

 free edges. The third thickens rapidly toward its posterior border. 

 Its greatest thickness is 10 millimeters; the greatest thickness of the 

 first is 4.5 millimeters. It extends inward from the free border 16 

 millimeters. The upper surfaces of all have growth lines on the 

 marginals, as shown in figure 1 on plate 36. All flare upward from 

 the costomarginal sulcus, toward the free border. 



The nuchal scute is wedge-shaped, the narrow end being forward. 

 On the free border it measures 2.5 millimeters in width; the porterior 

 end, 5 millimeters; length is 7 millimeters. 



The vertebral scutes are about as broad as long and rather imiform 

 in size. The sides are nearly parallel, with only a suggestion of being 

 bracket-shaped at the point where the costal sulcus is given off. 

 The principal dimensions of the vertebral scutes present are given in 

 the table: 



Measurements of vertebrals, in viillwieters. 



The first marginal is 18 millinietei"s wide, and extends mesiad 11 

 millimeters; the second and third, 15 miUimeters wide and 10 milli- 

 meters high, respectively. The sulci are moderately impressed, no 

 broad and deep as in the posterior peripherals of cotype No. 4061 

 U.S.N.M. 



The plastron has a greatest width at the center of about 80 milli- 

 meters. On account of the missing portions of the anterior and 

 posterior lobes its length can not be determined. The angular con 

 cavity of the inferior surface suggests that this specimen was a male 



The anterior lobe at its base had a greatest width of 60 millimeters 

 The notched sutural border at the center of the anterior ends of the 

 hyoplastrals shows the missing entoplastron to have been angularly 

 rounded behind. At this point the bone is 6 millimeters thick. 



The gulo-humeral sulcus reaches the posterior border of the 

 entoplastron but does not appear to have crossed that bone. In 

 this respect it agrees with the entoplastron of Emys pacliylomus Cope, 

 which is made a synonym of E. megaulax by Hay in his Fossil Turtles 

 of North America (p. 301). 



The bridge is 50 millimeters wide. The posterior lobe is 65 milli- 

 meters wide at the base and 40 millimeters in length at the center. 

 There is a median V-shaped posterior notch. 



The hypoplastrals meet on the midline for 28 millimeters; 

 hypoplastrals for 37 millimeters; xiphiplastrals for 23 millimeters. 



