1872.} 461 [Cope. 
Hyorsopus pyemaus. Cope. 
represented by a portion of the right mandibular ramus with the 
penultimate and ante-penultimate molars in perfect preservation. These 
teeth present four cusps, of which the inner are crescentoid in section, 
the outer conic. They are all elevated, and the outer anterior is in both 
teeth compressed and bifid ; it receives an oblique ridge from the inner 
posterior. Enamel smooth. 
Lines. 
Length penultimate molar. ................ eae Gy tee ee 
WHOtH ye Ne ee ee Hecaey cS cosae Re Meee res ib, 
Depth of ramus at do........ So aeey ad is socal eer oe iS 
This is a small species of the genus, being about equal to the Hyopso- 
dus paulus L. The penultimate molar in the allied species, Lophio- 
therium ballardii, Marsh, measures 3.2 lines in length. 
ANOSTIRA TRIONYCHOIDES. Cope. 
This species is about the size of our existing Chrysemys picta. It dif- 
fers from the A. ornata, Leidy, in various respects. Thus the sculpture 
of the costal bones is pit-like, as in some species of 7réonya, instead of 
striate-ridged. There is no keel on the pygal bone behind. The first 
marginal bone is longer, and does not exhibit the prominent shoulder 
seen in A. ornata. he marginal bones are not unlike those of that 
species, having central small tubercles, and radiating ridges. The species 
is not uncommon in the Bridger beds on Cottonwood Creek, Wyoming. 
ANOSTIRA GEDEMIA, Cope. 
This species is nearly twice the size of the last. It is distinguished by 
its peculiar ornamentation, This consists of bosses or swollen portions 
of an oval shape, which stand transversely to the long axis of the body, 
from a quarter to a half an inch apart. They sometimes form short 
ridges, surface otherwise smooth. Locality same as the last spogies. 
ANOSTIRA MOLOPINA. Cope. 
This species is intermediate in size between the two last described. 
It is distinguished from both by its ornamentation. This consists of a 
delicate and rather scattered impressed punctation, on the costal bones. 
Across this extend oblique ribs extending in a diagonal direction out- 
ward near the extremities of the costals. The width of one of the cos- 
tals is M. .023. The costals in this species display no suture for the mar- 
ginals, and the extremity of the rib projects a very little. 
TRIONYX CONCENTRICUS. Cope. 
This species is not uncommon in the Bridger sandstone. It is well 
characterized by its sculpture, which is coarsely and distinctly pitted. 
Across the costal bones run parallel ribs, which enclose between them 
from three to one row of pits. 
M. 
Width of a costal bone near the middle............... 02 
Thickness & ae S es eS . .008 
