106 FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL, i. 



Professor Cope has himself suspected that his genus Cynocercus 

 is identical with Toxochelys. If this is true the latter name becomes 

 a synonym of Cynocercus. This genus was founded on a metapodial 

 bone and some caudal vertebrae. As Professor Cope has observed 

 these vertebrae differ from those of the Chelydridce in being procoelous. 

 If the two genera referred to are identical, we have in these caudal 

 vertebrae an additional evidence of the relationship of our fossil to 

 the Cheloniidtz. 



In short, I conclude that Toxochelys is related both to the Chely- 

 dridce and the Cheloniidce, but that the relationship is much closer 

 to the last named family, and with the carnivorous division of this 

 family, Thalassochelys, etc. 



As to its systematic position, I agree with Dr. G. Baur's recent 

 statement that it should form the type of a new family. 



As to its phylogenetic relations, Toxochelys is probably an off- 

 shoot from the line which led to the Cheloniidx, an offshoot after the 

 latter family had disengaged itself from forms like the Chelydridce. 

 The skull of Toxochelys is too much modified in the direction of the 

 sea-turtles ever to be transformed into that of the modern snappers; 

 and the same remark will apply to the flattened phalanges, the prob- 

 ably greatly developed anterior limbs, and proccelous caudal vertebrae. 

 While there appears to be no special reason why Toxochelys might 

 not develop into a modern sea-turtle, we must remember that true 

 Cheloniidce had already made their appearance at the time when Tox- 

 ochelys left its remains in the upper Cretaceous deposits of Kansas. 



