352 University of Kansas Geological Survey. 



their relationships or validity are yet more or less problemat- 

 ical. 



The first known Testudinata are from the Upper Trias. Sin- 

 gularly enough these first turtles are as distinctly specialized 

 as those of the present time. The extraordinary specialization 

 which this branch of reptiles has undergone, whereby the ribs 

 have been transformed into a bony shell, and the shoulder and 

 pelvic girdles inclosed within the bony case, instead of being 

 outside the ribs, as in all other vertebrates, had been completed 

 by the close of the Trias. Undoubtedly we may expect the 

 early ancestors of the turtles, the more generalized forms with 

 incomplete carapace and with teeth in the jaws, at least as early 

 as the beginning of the Trias, if not in the Permian. So far, 

 however, all such evidence is wanting. 



In the Jurassic formation, turtles are very abundant and of 

 varied organization. In the Cretaceous, turtles have been found 

 in less abundance, yet they are not at all rare. The turtles of 

 the early Tertiary offer only slight differences from the Cre- 

 taceous Testudinate fauna. In the Eocene and Miocene lake 

 deposits of America the remains of often gigantic turtles are 

 very abundant. 



There is nothing in the history of the turtles that is of start- 

 ling interest. None have lived that were much larger than 

 some in existence. Protostega, from the Kansas Cretaceous, is 

 probably the largest. This form is peculiar in having a very 

 imperfectly ossified carapace, the ribs being separated and not 

 uniting into a solid bony plate. 



The classification of the turtles is by no means yet clearly 

 solved. The usual grouping is into three suborders — the Tri- 

 onychia, Cryptodira, and Pleurodira, The Trionychia include 

 turtles with a leathery skin, and not with horny shields, the 

 carapace poorly ossified and the body flattened. The soft-shelled 

 turtle of the Kansas rivers is an example. The Cryptodira in- 

 clude the great majority of turtles, such as the snapping turtle, 

 the tortoise, etc. The carapace and plastron are more or less 

 perfectly ossified, the head is withdrawn under the shell by a 

 vertical flexion, etc. All of the known forms from the Kansas 



