[O02 FOSSIL TURTLES OF NORTH AMERICA. 
The surtace of the bone is covered with rounded elevations which resemble small bird shot. 
There are about eight in a line 10 mm. long. The basis of each elevation is often of less 
diameter than the body of it. Many of them are broken off near the surface of the bone, 
leaving circular scars. Along the edges of the bone which joined the hyoplastra there is a 
narrow border nearly free from the pustules. 
This turtle differed from Polythorax missuriensis in the character of the ornamentation, 
this consisting in the latter species of short raised lines. In that species, too, the pectoro- 
humeral sulcus appears to have been pushed well forward. In the species here described 
there is no trace of the presence of this scute. 
Superfamily PLEURODIRA Cope. 
Thecophorous turtles having a carapace composed of costals and peripheral bones and 
usually a series of neurals and a plastron in which the epiplastra are in contact with the hyo- 
plastra. Mesoplastra present or absent. Intergular scutes developt, the inframarginals 
wanting. Temporal roof of the skull varying from nearly complete to nearly obsolete. Ptery- 
goids not extending backward between the quadrates and the basisphenoid; broad, with the 
outer border uprolled. Neck bending sideways; not capable of being withdrawn between the 
scapula. Ilia suturally joined to the eighth costals; the pubes and the ischia, to the xiphi- 
plastra. 
The living Pleurodira are divided by Boulenger into 2 families, the Pelomedusidz and the 
Chelydidz. About 30 species are known. None of these have had the anterior limbs trans- 
formed into flippers, like those of the Chelonude. The geographical distribution of the living 
species is illustrated by fig. 15, on page 34. The earliest turtles certainly known to belong to 
this superfamily occur in the Upper Cretaceous of North America. Cope referred these to the 
Pelomeduside; but the present writer, following Baur, accepts for them the family Bothremy- 
dida. So far as is known, no species of the superfamily lived in North America after the end 
of the Upper Cretaceous. 
Family BOTHREMYDID Baur. 
Extinct pleurodire turtles having the skull probably extensively rooft over in the temporal 
region. Vomer present. Triturating surfaces of the jaws, upper and lower, broad and deeply 
excavated. Shell as in the Pelomedusidz, with small mesoplastra. 
Baur was the author who proposed this family, making it include Bothremys and T aphro- 
sphys. Cope had arranged these genera under the Podocnemidida. To the present writer 
it appears that the presence of a vomer, but still more the extraordinary excavations found 
in the jaws, upper and lower, are sufficient to set off Bothremys as a member of a distinct family. 
With it must go for the present T aphrosphys. 
Kry To THE GENERA. 
A. Known from skull only: 
Each side of jaws, upper and lower, with a deep pit. : : Bothremys 
AA. Known from shell only: 
1. Nuchal bone not shortened; free borders of peripherals acute : .. Taphrosphys 
2. Nuchal short and broad; free borders of peripheral obtuse ; aa Ambly peza 
3. Only the xiphiplastron known; the ischiadic scar extending to the midline. . .. . Natadochel ys 
Genus BOTHREMYS Leidy. 
Vomer well developt, not separating the palatines. Choane behind the centers of the 
orbits. The nasal passages underfloored by the surrounding bones. Crushing surfaces of jaws 
broad and occupying portions of the manillz and of the palatines; the excavation contracting 
to a pit in each. Lower jaw with the dentaries co-ossified. Shell unknown. 
Type: Bothremys cook: Leidy. 
It has been suspected that the skull represented by the type of Bothremys is that of some 
species of Taphrosphys, all the species of which are known only from shells. This is entirely 
possible, but nothing is to be gained at present by reducing Taphrosphys to a synonym otf 
Bothremys. 
