DESMATOCHELYID^E. 



i8 S 



This genus is a most interesting one, inasmuch as it shows evident relationships with the 

 Cheloniidae, and at the same time presents characters which must be regarded as more primitive 

 than those of the latter family. Among these characters is the possession of well-developt 

 nasal bones. The choanae too have their primitive position just behind the premaxillae and are 

 separated by the body ot the vomer. In the Cheloniidae the latter bone sends downward a 

 perpendicular plate, the lower border of which expands laterally and joins horizontal plates 

 of the maxillae and of the palatines, forming a floor beneath the narial passages and pushing 

 the choanae further backward. The possession of small posterior palatine foramina shows a 

 closer connection with Amphichelydian stock than exists in the Cheloniidae, which have lost 

 these foramina. 



Williston thinks that the cervical vertebrae indicate pleurodiran characters. The posses- 

 sion of strongly developt transverse processes is to be regarded as an inheritance rather from 

 the Amphichelydia than from the Pleurodira. The articular ends of the cervical vertebrae 

 show decided affinities with the Cryptodira. An intervertebral articulation which is 26 mm. 

 wide and only 15 mm. high, belonging to a centrum only 26 mm. long, would not lend itself 

 readily to flexure sidewise, while it would permit easy flexure in a perpendicular plane. 



The Desmatochelyidae are to be arranged close to the Cheloniidae; but their many prim- 

 itive characters demand that they be kept in a distinct family. For those who are seeking a 

 Cretaceous ancestor for the modern sea-turtles, Desmatochelys presents itself as a more eligible 

 form than any of the Cretaceous Thalassemydidae. 



FIGS. 238 AND 239. Desmatochelys lowi. Skull of type. Xj. 

 238. Upper surface. 239. Seen from below. 



Desmatochelys lowi Williston. 



Figs. 238-243. 



Desmatochelys lowii, WILLISTON, Kansas Univ. Quart., Ill, 1894, p. 5; Univ. of Kansas Geol. Surv., 

 iv, 1898, p. 353, plates Ixxiii-Ixxviii. HAY, Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 443. 



The original and only known materials belonging to the present species are the property 

 of the University of Kansas. They consist of the skull, finely preserved, but lacking the hinder 

 part of the base; 3 cervical, the sacral, and some caudal vertebrae; the pectoral girdle, the 

 humerus, radius, and some metacarpal bones; most of the pelvic bones and an incomplete 

 femur; some fragments of the carapace and some of the plastron. The animal was apparently 

 preserved in fine condition, but was damaged in collecting. The remains were found in Benton 



