348 FOSSIL TURTLES OF NORTH AMERICA. 



emargination behind. Alveolar surfaces of upper jaw each with a longitudinal ridge, which 

 is somewhat denticulated and higher behind than in front. Choanae nearly as far back as a 

 line joining the middles of the orbits. Alveolar surface of the lower jaw with a longi- 

 tudinal groove, which is separated from a shallower groove by a longitudinal ridge. Symphysis 

 of lower jaw short, equal to about half of the distance between the quadrates. 



As type of this genus may be taken T. scripta, the species longest and best known and 

 incidentally the one mentioned first by Agassiz under the name. 



The species of this genus are allied to the species ot Chrysemys, but they attain a larger 

 size, possess a more vigorous organization, and a fiercer disposition. The wrinkled and 

 furrowed carapace, notcht posteriorly, distinguishes the species from those of Chrysemys. 

 The plastron has a quite distinct lip, and this is occasionally slightly dentated, but not so 

 conspicuously as in Chrysemys. 



The following analysis may aid in determining species ot which the nuchal bone is present: 



1. All the bones thin and little sculptured hilli 



2. Nuchal thick, strongly sculptured; free border broader than in T . sculpta, with notch 



for neural broader cuglypha 



?. Nuchal not so thick as in euglypha, about 15 mm.; free border rather obtuse sculpta 



4. Notch for first neural extremely broad jarmani 



5. Nuchal moderately thick, 10 mm.; width in front halt the maximum width petrolei 



6. Nuchal bone moderately thick; width in front three-fifths the maximum bisornata 



7. Epiplastral lip spout-like trulla 



Trachemys hilli (Cope). 

 Plate 55, figs. I, 2; text-figs. 451, 4^2. 



Pseudcmys hillii, Cope, Bull. Geol. and Geog. Surv. Terrs., iv, 1878, p. 395. 

 Trachemys hillii, Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 449. 



At the present time this species is represented by only the type specimen. This is in the 

 American Museum, as a part of the Cope collection of reptiles, and has catalog number 2425. 

 It was collected for Professor Cope in 1877, by Mr. R. S. Hill, in Decatur County, Kansas, 

 from Loup Fork deposits. It came, therefore, from the same locality and the same level as the 

 specimens of Testudo orthopygia. Since its arrival at the American Museum the fragments of 

 which the specimen was composed have been articulated under the supervision of the writer; 

 and the present appearance of the specimen is shown on plate 55. The shell has retained the 

 plastron complete, except that the entoplastron and the epiplastra are missing. Of the carapace 

 (plate 55, fig. 1 ; text-fig. 451) the peripherals are present from the rear to the fourth inclusive 

 on the right side and to the fifth inclusive on the left side. The third left peripheral also is 

 present. The nuchal is wanting. Only 3 complete neurals have been preserved, the fourth, 

 the fifth, and the seventh. A portion of the third is at hand. On the right side we have the 

 first, second, and fourth costals, and the proximal end of the third. On the left side there are 

 present the third, the fifth, and sixth costals, with a portion of the eighth. Both suprapygals 

 are wanting. 



The whole length of the shell was very close to 200 mm. The width at the hyohypoplastral 

 suture is 138 mm. The width of a specimen of T. rugosa, from some of the West Indian 

 islands, whose length of carapace is 192 mm., is 147 mm. It will be seen therefore that the 

 Loup Fork species is relatively more elongate. 



In elevation of shell this species resembles T. elegans or T. rugosa, rather than T. scripta, 

 the carapace being rather deprest. The maximum height from the bottom of the shell is 

 75 mm. 



The fourth neural has a length of 17 mm. and a maximum width equal to the length. 

 The fifth neural is 18 mm. long and 16.5 mm. wide. The sixth neural had a length of 15 mm. 

 and a maximum width of 16 mm. The second pygal was 27 mm. wide. 



Over the bridges a sharp keel intervened between the upper and the lower portions of the 

 shell. The free border of the third peripheral is acute. The posterior peripherals are only 

 slightly flared upward. Their free borders are thin and brought down to an acute edge. The 



