roxo< Ml- 1.1 ID.K. 



t6 7 



nearer then respective borders of the humerus. To the present writer the principal changes 

 which have affected the thalassic and parathalassic humeri, as represented by Caretta and 

 Dermofkelys,art to he found in the straightening of the shaft; the change of the head from a 

 position looking upward, in the natural position of the hone, to one looking toward the median 

 plane of the animal; the descent of the radial process, on the shaft; the transference of this 

 process, or of a component of it, toward the radial border; and the removal of the condvles 

 for the radius and ulna and of the ectepicondylar foramen or groove toward the ulnar border of 

 the bone. Of all these changes none seems to have taken place in Toxochelys, except a slight 

 descent of the radial process. In even other respect the bone retains the characteristics of 

 Chelydra. 



In main other features the fore limb of Toxochelys has made approaches to the flipper of 

 the marine turtles, as Dr. Wieland has shown. The ulna, as compared with that of Chelydra, 

 has become shorter relatively to the humerus while the radius has 

 become longer, as it has also to a greater degree in Caretta. The ulna 

 has become shorter than the radius, and the third and fourth fingers 

 have become greatlv elongated; but in these respects it is far behind 

 Caretta. The first and second fingers retain about the same ratio to 

 the humerus that thev have in Chelydra. Taken altogether, the limb 

 may be regarded as standing between that of Chelydra and the sea- 

 turtles but nearer to that of Chelydra. From the fact that the head of 

 the humerus had the position that it has in the freshwater turtles and 

 that the phalanges possest well-developt condyles we may be quite cer- 

 tain that the species of Toxochelys had no difficulty in getting about 

 on the land. 



The first and second fingers of Toxochelys were composed of 

 phalanges which were much stouter than those of the other fingers. 

 The terminal phalanges were encased in horn and formed strong 

 curved claws. The other fingers did not probably extend beyond the 

 border of the skin. Dr. Case (op. cit., plate lxxxii, figs. I, 2) repre- 

 sents the first finger as having 3 phalanges. This figure is evidently 

 that of the second finger. 



I he following measurements are taken from Dr. \\ ieland's des- 

 cription of the fore limb in Yale University Museum (fig. 200) : Length 

 of humerus, 135 mm.; radius, 75 mm.; ulna, 66 mm.; total length 

 of the first finger, 65 mm.; of second finger, 95 mm.; of third finger, 

 estimated, 150 mm.; of fourth finger, estimated, 135 mm.; of fifth finger, estimated, 90 mm. 

 The pelvis is somewhat more like that of Caretta than like that of Chelydra. Dr. Case 

 has given figures of the ilium (op. cit.. plate lxxxi., fig. 8 ) and of the ischium (op. cit., pi. Ixxxn, 

 fig. 6). The antero-lateral processes of the pubis are broader than they are in Chelydra. 

 The femur is not an uncommon bone in collections of Toxochelys materials. Figures of 

 the bone are presented by Case (op. cit., plate lxxxi) and Leidy (op. cit., plate xxvi, fig. 18). 

 Unfortunately the bone is usually crusht, so that its exact form is questionable. It is certain, 

 however, that the greater and the lesser trochanters were separated by a deep fossa, as Case 

 has described the bone. This fossa was probably like that found in Chelydra. In Caretta 

 and again in Testudo this fossa is nearly obsolete. Case believed that the femur was a weaker 

 bone than the humerus. This view is probably correct, and is corroborated by the relative 

 izes of the humerus and femur figured by Leidy. It is not certain, however, that these bones 

 belonged to the same individual. In Chelydra the femur is the longer bone. 



The tibia and fibula are not well known. There is presented in fig. 201 a portion of the 

 hinder limb in the possession of the author and believed to belong to Toxochelys. The tibia 

 and fibula are elongated and slender, more like those of Chelydra than like those of Caretta. 

 Four tarsals are present. The metatarsal is probably that of the first toe. Case (op. cit., p. 378 ) 

 describes the hind foot of an incomplete specimen, but the error is made of assigning four 

 phalanges to the first digit. The digit may have been the second, including the metatarsal. 

 The terminal claw was strong and much curved. The phalanges of the remaining digits wen 

 longer and slenderer, and the terminal one did not support a claw. 



Fig. 201. Toxochelys 

 sp. irtdet. ribia, fib- 

 ula, and some foot 



bones. 



X*. 



