G. R. Wieland — On Marine Turtles. lOT 



tliey may best be regarded as a subfamily, the Protosteginee. 

 Moi-eover, these Dermochelan resemblances are only what we 

 might well expect in Cretaceous turtles. There are likewise, 

 as we see, certain Chelydran resemblances in the general type 

 of skull, just as there are also Chelydran resemblances in 

 Toxochelys. ^e are simply following convergent lines back 

 sufficiently far to somewhat accentuate general relationships. 



Position of Toxochelys. The fore flip)per and cervicals of 

 Toxochelys present some additional Chelydroid characters to 

 those of the cranium and lower jaw, as already pointed out by 

 Cope and Hay. Toxochelys hence proves- to be one of the 

 most interesting of turtles. Like Protostega and Archelon, it 

 points with more or less distinctness toward a Chelydra-like 

 ancestry. Baur has said that this genus should be placed in a 

 distinct family, and in this has been followed by Hay and 

 Case. But I think that Toxochelys may more conveniently be 

 considered as representing a subfamily of the Chelonid?e, cer- 

 tainly if of common ancestry. 



y. Provisional classification of the marine Testudinates. 



Chelonioidea (Baur). 



(Superfamily of the Cryptodira.) 



A parieto-squamosal arch ; palatine foramen and free nasals 

 sometimes present (Desmatochelydinae); fourth cervical bicon- 

 vex, with the centra of the sixth, seventh, and eighth usually 

 greatly moditied. 



I. DermochelycJidce. 



No descending parietal processes ; no palatine foramen ; 

 other cranial and limb characters not remote from those of the 

 Chelonidse ; carapace represented by the nuchal only, and body 

 enveloped in a leathery hide with an osteodermal mosaic ; no 

 claws. Genera : Dermochelys^ Psejyhoj^horous., Eosj^hargis. 



II. ChelonidcB. 



Skull with descending processes of parietals, so far as 

 known ; palatine foramen sometimes present ; vomero-premax- 

 illar union often, but not constantly present ; a normal, though 

 often much reduced, carapace and plastron ; nuchal with or 

 without process on under side ; claws, one or two. 



1. Protosteginse. — ISTo free nasals ; no palatine foramina ; 

 obturator foramen small and enclosed by ischiopubic contact 

 on median line, as in many land forms. 



Genera: Protostega 2ind Archelon ; Protos^hargisf Pseu- 

 dosphargis f 



