180 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. 
On 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 ( I wieland1). 
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 vertebra and a medapodial. Caudals proceelous and provided 
with chevrons. The articular cup with a median perpendicular groove or incision. 
Type: Cynocercus incitsus Cope. 
This little-known genus is placed in the present family because of the possibility that it is 
identical with Toxochelys. 
Cynocercus incisus Cope. 
Cynocercus tnctsus, Cope, Proc. Amer. Philos. Soc., x11, 1872, p. 308; Proc. Acad. Nat. Sci. Phila. 1872, 
p. a Be Ann. Report U. S. Geol. Sury. Mont., ete., 1871 (1872), p. 335; Vert. Cret. Form. 
West, 1875, pp. 96, 260, plate viii, figs. 3-5. —Wiuiston, iinet Geol. Surv. Kansas, tv, 1898, 
p. 368, He 6.—Hay, Pubs. Field Colum. ‘Museum, Zool., 1, 1896, p. 106; Bibliog. and Cat. Foss. 
Veet N. Avesl O02 aipin4 42, 
Cynocercus incisus was based on two caudal vertebra 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 vertebra 
is 27 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 Aram Figse of Chelydra in being proceelous. They differ further from those of the latter 
genus in being more comprest and in having higher neural arches. Cope suggested a resem- 
Bec to those of the Trionychoidea. Brom fhe latter they differ in possessing chevrons and 
in having the transverse processes attacht to the centrum. ‘The vertebrz of the anterior half of 
the tail of soft-shelled turtles have high neural arches; from these spring transverse processes. 
What appears to distinguish fice caudals from those of any other known genus is the 
presence of a sharp grooye, or incision, running perpendicularly down the middle of the articu- 
lar cup. It has Been suggested by more dian one author that these vertebre are those of 
some species of Toxoc helye: but this has not yet been proved. 
Genus PORTHOCHELYS Williston. 
Skull as broad as long. Nasal bones present. Lateral fontanels of the carapace obsolete. 
All of the peripherals articulating closely with the costals. No carina along the middle of the 
back and no tubercles. Plastron with small median and lateral fontanels. 
Type: Porthochelys laticeps Williston. 
Porthochelys laticeps Williston. 
Plate 31, figs. 2, 3; text-figs. 231-234. 
Porthochelys latice ps, ee Trans. Kansas Acad. Sci., xvit, B, 1901, p. 195, plates xvili—xxil. 
Hay, Bull. Amer. Mus. Nat. Hist. xx1, 1905, p. 183. 
The 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 
oreater portion of the skull, nearly the whole of the left side of the carapace, the whole of the 
