370 University of Kansas Geological Survey. 



TOXOCHELYS. 



BY E. C. CASE. 



Toxochelys is the single well-established genus of the sea 

 turtles from the Cretaceous of Kansas comparable to the living 

 Oheloniidse. In habit of body the species were very similar to 

 those of the genera Chelonia and Thalassochelys. The head was 

 low and flat, roofed posteriorly by the bones of the skull, and 

 provided with the large orbits characteristic of the family. The 

 limbs were modified as swimming organs, especially the front 

 pair, which were developed into long, powerful flippers. It is 

 probable that these turtles spent the larger part of their time in 

 the open seas, seeking the beaches only to deposit their eggs. 

 The different species of the genus varied in size from about two 

 feet in T. serrifer to five or six in T. latiremis. 



The genus was founded upon the characters of the lower 

 jaw, the coracoid, and phalanges. In a second description of 

 the genus Cope says (Cret. Vert. 98) : " The mandibular 

 ramus is slender, and has a narrow, flat, alveolar surface. The 

 coronoid process is moderately elevated, and is excavated be- 

 hind by the anterior extremity of the elongated and deep dental 

 foramen. The cotylus is depressed, and the articular bone 

 ossified. The angle is not produced. The coracoid bone is 

 long and spatuliform, like that of the marine turtles." 



"The slenderness of the mandibular rami resembles the form 

 in Chelydra, but it differs in the absence of the alveolar cutting 

 edge of the latter. The phalanges are broad and flat and not 

 unlike those of Protostega ." 



While primitive in many of its characters, Toxochelys was al- 

 ready well advanced in the line towards the modern Cheloniidse. 

 Cope believed that it was related to this family and to the 

 Chelydrids?. Hay thought that it is "related both to the 

 Chelydrida? and the Cheloniida^, but that the relationship is 

 much closer to the last-named family, and with the carnivorous 

 division of this family, Thalassochelys." 67 



67. Hay, O. P., Field Columbian Museum Publications. 12 and 13, Zool. Series, vol. i, 101, 

 pis. xiy and xv. 



