iSo FOSSIL TURTLES OF NORTH AMERICA. 



border; a maximum width of" 145 mm. Its fore-and-aft extent is 55 mm. The table gives the 

 dimensions of the peripherals. The width is taken at the notch of each where the sulcus crost 

 the free border. 



( >n account of considerable crushing the thickness has not been given. We are informed 

 by Wieland that transverse sections are approximately as in the peripherals of Lytoloma 

 angusta ( = L. wielandi). 



The pygal measures 65 mm. along the free border and 45 mm. along the midline. 



The reader is referred to page 165 for remarks on the connection of the rib of the eighth 

 costal plate with the eleventh peripheral of this species. 



Genus CYNOCERCUS Cope. 



A genus based on caudal vertebrae and a medapodial. Caudals procoelous and provided 

 with chevrons. The articular cup with a median perpendicular groove or incision. 



Type: Cynocercus incisus Cope. 



This little-known genus is placed in the present family because of the possibility that it is 

 identical with Toxochelys. 



Cynocercus incisus Cope. 



Cynoi 1 n us in, isus, Cope, Proc. Amer. Philos. Soc, xn, 1872, p. joS; Proc. Acad. Nat. Sci. Phila. 1872, 

 p. [29; I itrli Ann. Report U. S. Geol. Surv. Mont., etc., 1 87 1 (1872), p. 355; Vert. Cret. Form. 

 Wist, [875, pp. 96, 260, plate viii, figs. 3-5. Williston, Univ. Geol. Surv. Kansas, iv, 1898, 

 p. 568, fig. 6. Hay, I'ubs. Field Columb. Museum, Zool., I, 1896, p. 106; Bibliog. and Cat. Foss. 

 Vert. V A.. [902, p. 442. 



Cynocen us incisus was based on two caudal vertebrae and a metapodial. These were 

 found by Cope in the yellow chalk, probably the Niobrara, near Butte Creek, south of Wallace, 

 Kansas. These bones are now in the American Museum of Natural History and have the 

 number 1582. It is not known whether the metapodial belongs to the fore or the hinder foot. 



The vertebrae were fully described and figured by Cope as cited above. Williston repro- 

 duced a portion of the description and the figures of the vertebra?. The reader is referred to 

 these authors. It may be here stated that the length of the centrum of each of these vertebrae 

 is 2/ mm., a fact showing that the animal must have been of considerable size. They did not 

 belong among the most anterior, for they possest chevrons. Cope stated correctly that they 

 differ from those of Chelydra in being procoelous. They differ further from those of the latter 

 genus in being more comprest and in having higher neural arches. Cope suggested a resem- 

 blance to those of the Trionychoidea. From the latter they differ in possessing chevrons and 

 in having the transverse processes attacht to the centrum. The vertebrae of the anterior half of 

 the tail of soft-shelled turtles have high neural arches; from these spring transverse processes. 



What appears to distinguish these caudals from those of any other known genus is the 

 presence of a sharp groove, or incision, running perpendicularly down the middle of the articu- 

 lar cup. It has been suggested by more than one author that these vertebrae are those of 

 some species of Toxochelys; but this has not yet been proved. 



Genus PORTHOCHELYS Williston. 



Skull as bioad as long. Nasal bones present. Lateral fontanels of the carapace obsolete 

 All ol the peripherals articulating closely with the costals. No carina along the middle of the 

 ba< k and no tubercles. Plastron with small median and lateral fontanels. 



I ype : Porthochelys laticeps Williston. 



Porthochelys laticeps Williston. 

 Plate 31, figs. 2, 3; text-figs. 231-234. 



Porthochelys laticeps, Williston, Trans. Kansas Acad. Sci., xvn, B, 1901, p. 195, plates xviii-xxii. 

 Hay, Bull. Amer. Mus. Nat. Hist, xxi, 1905, p. 183. 



I he type of this fine species is the property of Kansas University and was collected in the 

 Niobrara beds, on the Saline River, in Trego County, Kansas. The remains comprize the 

 greater portion of the skull, nearlj the whole of the left side of the carapace, the whole of the 



