262 FOSSIL TURTLES OF NORTH AMERICA. 



agonal, with the broader end forward; the third being 56 mm. long and 25 mm. wide; the 

 fourth, 46 mm. long and 22 mm. wide; the fifth, 38 mm. long and 22 mm. wide. The sixth is 

 hexagonal, 20 mm. long and 28 mm. wide. The seventh neural is pentagonal, 22 mm. long and 

 17 mm. wide. It has the appearance of having been crowded far forward out of its place. 

 There is a single broad suprapygal whose length is 46 mm. and width 100 mm. 



The members of the sixth, seventh, and eighth pairs of costals respectively meet along 

 the midline. The suture between those of the eighth pair is 82 mm. long. The peripherals 

 are unusually high, about 100 mm. along the sides; somewhat less toward each extremity of 

 the animal, the first and eleventh being about 64 mm. high. The free peripherals are thin at 

 the borders, and the hinder ones are reduced to a sharp edge. The thickness of the second 

 peripheral, near the upper border, is 20 mm.; that of the ninth, at the upper border, is 16 

 mm. There are 1 1 of these peripherals on each side. 



As stated, it is difficult, in a few cases impossible, to determine satisfactorily the bound- 

 aries of the epidermal scutes. In front there is a very narrow nuchal, about 10 mm. wide 

 and 20 mm. long. This is followed by a first marginal, 58 mm. along the front edge and 

 30 mm. fore and aft. The sulci between the marginals and the costal scutes appear to run at 

 a considerable distance below the sutures between the costal and peripheral bones, the mar- 

 ginals being about 75 mm. high. The limits of the vertebral scutes are satisfactorily deter- 

 mined, except those of the fifth. The first vertebral is 80 mm. long and 130 mm. across its 

 anterior end. The second is 100 mm. long and 65 mm. wide; the third 90 mm. long and 66 mm. 

 wide; the fourth apparently 108 mm. long and close to 58 mm. wide. The fifth was probably 

 1 15 mm. long and about 130 mm. wide. 



The surface of the carapace, including the lower faces of the peripherals, is ornamented 

 with narrow and low longitudinal wrinkles of which there are from five to eight in a 10 mm. 

 line. They are possibly due to the great age of the specimen and may be wanting in the 

 younger individuals. 



The plastron (plate 39, fig. 2; text-fig. 324) is well developt, altho it leaves wide spaces 

 between it and the carapace. It was apparently quite flat, altho now somewhat concave 

 transversely, the result possibly of pressure. The total length is 415 mm. The anterior lobe 

 projects nearly as far forward as the anterior border of the carapace; but the hinder fails to 

 extend as far backward as the carapace by about 115 mm. The anterior end of the plastron 

 is very slightly emarginated; the posterior end is broadly rounded and without notch. 



The length of the anterior lobe is 100 mm.; its width at the axillary notch 209 mm. It 

 decreases in width gradually at first, then rounds rapidly to the notch in front. Its thickness 

 near the front is 9 mm. The length of the posterior lobe is 132 mm.; its width at the inguinal 

 notches is 190 mm. The bridge is 180 mm. in width. The axillary and inguinal buttresses 

 do not appear to extend inward beyond the adjacent borders of the plastron. 



The entoplastral bone is short and broad and with a nearly straight hinder border. Its 

 length is 55 mm; its width, 90 mm. The hyoplastral bones meet along the midline for a dis- 

 tance of 100 mm. The suture separating the hypoplastrals from the xiphiplastrals is believed 

 to be placed as shown in the figures. The former bones occupy 135 mm. of the midline; the 

 latter, 84 mm. 



Gular and intergular scutes seem to be present and to have the positions and forms given 

 them in the figures. The intergular area is evidently divided by a median sulcus. The two 

 taken together are 75 mm. wide and 50 mm. long. The gulars are small, triangular, and 

 widely separated by the intergulars. 



The humero-pectoral sulcus crosses the midline at the hinder end of the entoplastron. 

 The humerals meet on the entoplastron for a distance of 48 mm. The pectorals extend 

 along the midline only 46 mm. Altho the femoro-abdominal sulcus is not as distinct as 

 might be desired, it is probably placed correctly in the figures. The abdominals thus have a 

 fore-and-aft extent of 128 mm. The femorals extend along the midline 80 mm.; the anals, 

 67 mm. 



On the bridges of the plastron there are at least four inframarginals. Of these, the one 

 in front is small and square; the second, pentagonal; while the fifth is probably hexagonal. 

 The third is 95 mm. long and 42 mm. wide, and may possibly be subdivided; but no sulcus 

 is visible. 



