530 FOSSIL TURTLES OF NORTH AMERICA. 
The sculpture of the carapace was of moderate coarseness. On the distal halves of the 
costals the pits are in rows parallel with the free border of the costal, and there are five of these 
rows in a line 20 mm. long. Proximally the pits are no longer in rows and are larger, 3 or 4 
in the distance named. Aihe sutural borders of the costals are striated across the sutures. 
Fig. 690 represents the known bones of the plastron. A portion of the hyoplastron is miss- 
ing, Nine it is quite certain that the outer end has been placed very close to its proper position. 
This bone had an extent laterally of about 252 mm., not including the antero-external spine. 
It is remarkable for the narrowness of the end next the midline, this being only 60 mm. The 
width at the bridge was about 52 mm. ‘The greatest thickness of the bone is about 17 mm. 
The outer end of the hypoplastron is wanting, as well as the hinder border of the bone. The 
bottom of the notch receiving the inner process of the xiphiplastron is present, so that the form 
of the hypoplastron given in the drawing is not far from correct. The width at the narrowest 
part of the bridge is 37 mm., being thus less than that of the hyoplastron. The thickness at 
the bridge is 21 mm. 
On account of the advanct age of the individual, the layer of the bone forming the 
“callosities” extended itself to the ents of the processes at the midline. The lower surface of the 
plastral bones is nearly smooth, but shows everywhere the vestiges of pits and ridges. Where 
distinct enough to be perceived they seem to have been smaller than those of the carapace. 
The sculpture of the carapace of this species resembles that of dmyda uintaénsts, consisting 
of large pits at the proximal end of each costal and somewhat smaller ones in rows at the distal 
end. Those of 7. manducans are, however, somewhat larger, in corresponding situations. 
The shell, too, is thicker. The greatest differences are found in the plastra of the two species. 
In 4. wintaénsrs the inner end of the hyoplastron is two and a half times as wide as the nar- 
rowest portion at the bridge; whereas, in J. manducans the two portions are of nearly the 
same width. The front border of 4. wintaénsis was quite concave, while that of T. manducans 
was nearly straight. It is not probable that such differences can be due to difference in age. 
The type of 4. wintaénsis is about four-fifths as large as that of the present species. 
From dAmyda scutumantiquum the present species differs in the same way that it does 
from A. uintaénsis; that is, in the narrowness of the inner end of the hyoplastron. A. radula, 
whose nuchal has a similar thickened anterior border, differs in having a thinner shell, the 
free borders of which are beveled, and in having a finer sculpture. 4. egregia has a thicker 
shell, a coarser sculpture, and no overhanging layer at the free borders. 4. cariosa, of the 
Wasatch of New Mexico, evidently had eich deeper and more abrupt pits on the proximal 
ends of the costals. The bone regarded by Cope as a xiphiplastral was deeply pitted, a con- 
dition not to be expected in T. ee Sen Aspideretes guttatus has a different sculpture 
and a relatively broader bridge. Aspideretes ellipticus had a nuchal whose anterior border 
was beveled off on the upper surface. 
Genus PLATYPELTIS Fitzinger. 
Carapace with the eighth pair of costals wanting or greatly reduced. No preneural. One 
or two of the posterior pairs of costals may be in contact on the midline, or all may be separated. 
Young in the living species with smooth or granulate skin. 
he type of rhe genus Platypeltis is Te niu ferox Schneider (=Trionyx ferox of Boulen- 
ger’s Catalogue). He known living species are all inhabitants of America. 
Key tro Fosstt Species oF PLATYPELTIS. 
A‘. Puerco or Torrejon species: 
1. Nuchal probably loosely attacht to first costals. No welts on carapace. Six pits 
in a line 10mm. long....... : Oe, teoe. ere eos PMR eco a Mes ainsi ene antiqua 
*. Wasatch species: 
Disk of carapace not as wide as long; with ribs projecting far beyond disk. 
Nuchal probably loosely connected with its costals and neural; sculpture coarse, 
tS 
t 
Wit WEltS ys. < siace'Sts a's CWS re ste eats Ore, ee ee eee ee sertalts 
2. Sculpture coarse, especially on proximal ends of the costals, but without welts. 
Anterior border of hyoplastron concave............... So ae ope eahsgiies eae) ca aE amnicola 
A’. Bridger species: 
1. See AY eee : PERE Ee et ects ae ee sertalis 
. Nuchal sutured to first cost: tals; welts not t conspic uous; 5 to 7 pitsinIOmm.... tre ptda 
