210 FOSSIL TURTLES OF NORTH AMERICA. 



Cope arranged this genus among his Propleuridae. The cordate form of the carapace 

 in the state collection at Atlanta, deeply excavated in front and pointed behind, appears to 

 indicate close relations with the Cheloniidae, and to this family the species is here provisionally 

 assigned. 



Peritresius ornatus (Leidy). 



Chelone ornatus, Leidy, Proc. Acad. Nat. Sci. Phila. 1856, p. 303; Smithson. Contrib. Knowl., xiv, 



1865, pp. 105, 119, plate wiii, hg. 10. 

 Peritresius ornatus, Cope, Cook's Geol. New Jersey, 1868 (1869), p. 735; Amer. Naturalist, in, 1869, 



p. 88; Ext. Batrach., Reptilia, Aves N. A., 1870, p. 150; Vert. Cret. Form. West, 1875, p. 260; 



Amer. Naturalist, ill, 878, p. 129. Hay, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 441. 



This is yet an imperfectly known species. It was based by Leidy on conjoined portions 

 of two lateral peripherals, which had been found in Cretaceous greensand in Burlington 

 County, New Jersey. This greensand probably, but not certainly, belonged to the upper 

 bed. The bones are probably now in the collection of the Philadelphia Academy, but they 

 have not been seen by the present writer. They were described by Leidy as measuring an 

 inch and a half in breadth and as being wedge-shaped in section. The outer border was 

 acute; the inner border grooved, and eight lines, about 17 mm., high. Both the upper and the 

 lower surfaces were coarsely, but beautifully, tuberculated, and the tubercles showed a tendency 

 toward a radiate arrangement. Some of the tubercles at the ends of the peripherals are 

 lengthened out into ridges. Cope states that there were no indications of dermal sulci on the 

 bones. He mentions also a costal which he thought belonged at least to the genus. 



Under the species Taphrosphys nodosus the present writer has suggested that it may be 

 identical with the species here described. 



In the collection ot the Geological Survey of Georgia is the greater portion of the carapace 

 of what appears to have been a large sea-turtle. This specimen was at one time in the hands 

 of Prof. E. D. Cope and was by him identified as Peritresius ornatus Leidy (Amer. Naturalist 

 111, 1878, p. 129). Considering the facts that Leidy's type consisted of portions of two 

 evidently hinder peripherals and that all the hinder peripherals of the Georgia specimen are 

 wanting we can not be sure that the identification is correct. For the present it may be allowed 

 to stand. Undoubtedly it was on this specimen that Cope based his definition of the genus 

 Peritresius. It is not known why Cope concluded that there were 9 pairs of costals. 



The specimen here described was found by Mr. Loughridge, of the Georgia Geological 

 Survey, then under the direction of Dr. George Little, in the Ripley formation of the Upper 

 Cietaceous,on Bonnahachee Creek, Stewart County, Georgia. It presents most of the carapace, 

 but unfortunately the left side is yet concealed by a mass of matrix. This has prevented an 

 accurate study of the specimen and the production of a figure. The length of the portion pres- 

 ent is 675 mm. in a straight line, 735 mm. over the curve. The original length of the carapace 

 must have been about 900 mm. In form the carapace is cordate, like that of Caretta. Anteriorly 

 there is an excavation in the border 200 mm. wide and about 30 mm. deep. The free border is 

 obtuse and the bone is about 16 mm. thick. The costals are about 8 mm. thick. The anterior 

 peripherals are suturally joined to the first costals. Behind this they are missing; but it is 

 evident that some of them were connected with the costals only by gomphosis ot the ribs. 



I he most conspicuous feature of the carapace is the great dorsal keel. This begins on the 

 nuchal bone and continues to the rear of the carapace. It is thick and obtuse on the anterior 

 half of the carapace. Here the sloping sides of the keel are very steep, the summit is obtuse, 

 and the height is about 36 mm. Posteriorly the summit is more acute. 



On account of the great number of fractures it is difficult to follow the sutures. Where 

 observed these are coarse and zigzag. A few of the sulci are traceable. The third vertebral 

 scute has a width of about 125 mm. The sulci forming its lateral boundaries are nearly parallel 

 with the axis of the animal. 



The whole upper surface "f the carapace is coarsely pitted and ridged, much like that of 

 some species of Trionychida;. 5 or 6 ridges are usually to be counted in a line 25 mm. long. 



The anterior border of a second specimen is in the same collection. Found with it is the 

 greater portion of the united dentary bones. The triturating surfaces are flat. The length 

 of tin- symphysis is 53 nun. 



