144 



FOSSIL TURTLES OF NORTH AMERICA. 



The area of the scutes of the carapace is distinctly markt. The nuchal scute measures 

 58 mm. along the free border; 90 mm. along the posterior border. Fore and aft it is only 20 mm. 

 The first vertebral had a width of about 200 mm. Its length was 100 mm. The second vertebral 

 was 100 mm. wide and 150 mm. long. Behind the first peripheral the costo-marginal sulcus 

 ran along the unossified space between the costals and the peripherals. 



The plastron evidently had the form presented in O. gtbbi. The piece of the bone consid- 

 ered by Cope as the epiplastron is the anterior outer end of the hyoplastron. At the axillary 

 notch the hyoplastron had a thickness of 1 1 mm. At the inguinal notch the hypoplastron was 

 14 mm. thick. As in the other species, there was an interchange of digitations between the 

 hypoplastron and the xiphiplastron. 



Cope figured the right humerus. This bone lacks the head, both trochanters, and a little 

 of the distal end. The original length must have been close to 120 mm. The radial and the 

 ulnar crests made apparently something more than a right angle with each other. The shaft 

 is bent and flattened. The dorso-ventral diameter is 13 mm.; the horizontal diameter, 19 mm. 

 The width of the distal end is 38 mm. The femur is practically complete. The extreme 

 length is 132 mm. The bone resembles closely that of Chelydra. The planes of the tibial and 

 the fibular crests make a right angle with each other. The diameter of the shaft is 14 mm.; 

 that of the distal end, 36 mm. 



In the American Museum of Natural History are portions of a large individual which is 

 referred to this species. There are present peripherals 7 to 1 1 inclusive of the left side, periph- 

 erals eight, ten, and eleven of the right side, and a considerable part of the hindermost 

 suprapygal. With these are other bones, some or all of which may belong to another individual, 



possibly to another species. These con- 

 sist of 2 complete costals, 3 neurals, the 

 left hyoplastron lacking the inner end, 

 the left hypoplastron lacking a small 

 portion of the outer end, and a femur. 

 Besides these, there are parts of first, 

 second, and third suprapygals that can 

 not belong to the same individual as 

 did the peripherals. All these bones 

 are included under the number 1132. 

 This is the specimen mentioned by Cope (Ext. Batr., Rept., etc., p. 142) as having been 

 found at Hornerstown, Monmouth County, New Jersey. 



The peripherals (plate 26, fig. 3) indicate a large individual, with a carapace about 825 mm. 

 long. The dimensions of the peripherals are given in the table above, the measurements 

 being taken as in the case of the type specimen. 



The pits for the rib-ends entering the hinder three peripherals are flattened, as in the No. 

 2351, and similarly they notch the upper face of the bones. None of the peripherals present 

 was suturally articulated with the costals, but the eleventh was sutured with the hindermost 

 suprapygal. The latter had a length of about 75 mm. and a width of 180 mm. It was there- 

 fore quite different from that of 0. gibbi. 



A fragment that must have belonged to another individual presents the first, second, and a 

 part of the third suprapygals, and a part of the eighth costal. The first suprapygal is about 

 40 mm. long and the width is the same. The second suprapygal has a length of 45 mm. and 

 a width, along the nearly straight hinder border, of about 130 mm. Of the third there is only 

 a small piece. The first suprapygal is crost by the sulcus between the fourth and the fifth 

 vertebral scutes. 



One of the costals is probably the third of the right side. It has a length, over the curve, of 

 about 275 mm., not including the projecting rib-end. The breadth near the proximal end is 

 87mm.; near the distal end, about 95 mm. The thickness at the sutural edges is 7 mm. The 

 distal end had not been sutured with the peripherals. Articulated with this costal is a neural, 

 probably the third. Its length originally was about 90 mm.; its breadth anteriorly is 58 mm. 

 The posterior end is narrowed and rounded. The costal and this neural supported portions 

 of the third and fourth vertebral scutes. The fourth, at the hinder border of the costal, had a 

 width of about 140 mm.; the third was apparently slightly narrower. 



