428 



FOSSIL TURTLES OF NORTH AMERICA. 



The length ot" the carapace of this individual is 930 mm.; the greatest breadth, 690 mm. 

 Thru pressure of the overlying matrix the carapace is somewhat deprest, so that the form 

 of the shell is best shown by the type of the species. The length of the plastron is 840 mm. 

 The anterior lip projects hardly as much as in the type, a smaller individual. 



This specimen displays beautifully the armor of the forelegs. A closely compacted layer 

 of bony nodules was imbedded in the skin, from the bases of the claws to the middle third of 

 the upper arm bone. Along the ulnar side of the forearm is a row of larger nodules, one of 

 which appears to have been formed by the co-ossification of two originally distinct bones. 

 Some of the larger nodules appear at the elbow joint. Above this the nodules decrease in size. 

 The palm of the hand was protected by a layer of bones of moderate size. Beyond the bones 

 forming the armor of the foot projected the five claws. 



The hind foot possest a sole of bony nodules, but those bones shown in the figure near the 

 claws are the phalanges. Toward the hinder border of the foot the nodules become larger 

 and the two hindermost project as great spurs. Such bony spurs armed with a covering of 

 tough horn would doubtless offer some discouragement to any carnivorous animal that might 

 have sought entrance in that region. Perhaps also these spurs would be of assistance to the 

 animal in walking over a rocky surface. Another great spur lies alongside the fourth claw 

 phalange and simulates a fifth claw. In the type specimen, No. 5868, the fifth tarsal bone of 

 the second row shows an articular surface for a rudimentary metatarsal. 



The tail presents in general the same features as that of the type specimen. The central 

 nodules are still more intimately consolidated. The lower border of the armor covering the 

 tail was apparently 140 mm. wide, and was bordered by about 10 nodules, which increase in 

 size from the midline each way. The outer 3 are pointed. It was probably just outside of 

 these that the armor of the tail past into that covering the thighs. In this specimen this armor 

 is continued two-thirds the distance to the knee-joint. On each side of the tail are two very 

 large and pointed spurs, such as we find on the thigh of various living species of Testudo; but 

 these in T . osborniana appear to have been placed nearer the tail than usual. In the type 

 specimen there appears only one spur on each side of the tail. 



The scapula and its proscapular process are slenderer than those of T . tmpensa. The 

 type of the latter has a carapace only a few millimeters shorter than the specimen of T. osborn- 

 iana here described. The table presents the dimensions of certain parts of the two species. 



Measurements taken. 



Diameter of procoracoid process at middle of length: 



Greater 



Smaller 



Length of coracoid from glenoid to median border .... 



Length of median border of coracoid 



Length of humerus from middle of head to distal end . . 



Least diameter of shaft 



The ulna is hidden beneath the armor. The right radius is exposed sufficiently to permit 

 determination of the length. This amounts to 135 mm. 



The skull of this individual was considerably macerated about the time of burial; the 

 bones have been more or less fractured and sometimes slightly displaced. One important differ- 

 ence is shown between it and the skull of the type; namely, the interorbital space is much 

 broader. In the type this space is 28 mm. wide; in the one now described it is 43 mm. Ordi- 

 narily this difference would be regarded as indicating a distinct species. Here we have prob- 

 ably a difference due to sex. The type is almost certainly a male, as is shown by the very 

 concave plastron. The other individual has a very flat plastron and was probably a female. 



The cervical vertebrae are all present. The elements of the first are hidden beneath the 

 supraoccipital process. The second has been damaged so badly that little can be said regarding 

 it, but the posterior end appears to have been concave. The third seems to have had a convex 

 anterior end. Its posterior end is concave. The fourth has the anterior end convex. The con- 

 tiguous ends of the fourth and fifth are injured, but it seems pretty certain that the hinder end 

 of the fourth was convex and the anterior end of the fifth concave. The sixth is concave in 



