104 FOSSIL TURTLES OF NORTH AMERICA. 
ally, the pterygoids are wide, and the outer border is uprolled in a scroll-like manner. The 
basisphenoid, most of which is present, is large, the width being 13 mm. 
The most striking feature of the skull is presented by the triturating surfaces of the upper 
jaws. On the premaxilla they are very narrow. Backward each expands rapidly and occupies 
most of both the maxilla and the palatine. The greatest width is 24 mm. Each, instead of 
being flat, is deeply excavated. At the suture between the maxilla and the palatine the exca- 
vation contracts into a circular pit which rises in the maxilla to the height of the floor of the 
orbit. The walls inclosing this pit are smooth. The remainder of the triturating surface is 
perforated by openings for blood-vessels. 
The lower jaw shows little else than the co-ossified dentaries. “These are of very solid 
construction. ‘The jaw as a whole is thin and pointed in front, but the coronoid processes rise 
toa height of 27 mm. The sy mphysis has a length of 20 mm. The triturating surfaces are as 
pcracricaple as those of the upper jaw. Each may be described as containing a deep pit, 
situated at the hinder end of the dentary and opening forward and upward, trumpet-like, on 
the upper surface of the dentary. The trumpet-shaped mouth extends forward to near the tip 
of the jaw. It is bounded outwardly by the cutting-edge of the J jaw; inwardly by a ridge, which 
rising at the tip of the jaw, runs backward and upward, increasing in height to the coroner’ 
process, along the inner border of the ramus. 
The purpose of the pit-like excavations in the jaws, upper and lower, is problematical. 
In speaking of the pit in the upper jaw Leidy said that it did not appear like an alveolus for a 
tooth, but that it may have accommodated a corneous tooth-like process springing from the 
corresponding hollow of the lower j jaw. Baur thought that the pits lookt much like the alveoli 
of large tusk-like teeth. 
It does not appear probable that there were any teeth in this turtle. It seems far more 
probable that both jaws were covered with plates of horn, as are those of all other known 
turtles. The whole construction of the skull of Bothremys indicates that it was accustomed to 
crush hard objects as food. Probably these objects were of such a nature that economy of 
force demanded that they should be brought to a particular spot on the jaw for crushing. To 
provide for the rapid reproduction of the horn beneath these areas for crushing, these pits 
became developt in a way analogous to the human “‘nail-bed.” 
Genus TAPHROSPHYS Cope. 
Prochonias Cope. 
A genus of pleurodirid turtles known only from the shell. Carapace with 7 neurals, the 
costals of the seventh and eighth pairs meeting their fellows at the midline; a large suprapygal; 
and 11 pairs of peripherals, the posterior thin and with acute free borders. No nuchal scute. 
Plastron with 11 bones, the mesoplastrals small and well out on the bridges. A single intergular 
almost wholly confined to the entoplastron. Hinder lobe with large notch. Large pits in the 
first and the fifth costals for the axillary and inguinal buttresses. Ilium firmly articulated with 
the carapace at the junction of the seventh and eighth costals. Ischium and pubis articulated 
to the xiphiplastron. 
Type: Platemys sulcatus Leidy. 
In Cook’s Geology of New Jersey, 1868 (1869), page 735, Cope mentions the generic name 
Taphrosphys in connection with 3 specific names, as follows: J. molops, T. princeps, and 
T. sulcatus, The first two had not yet been described, the last was Leidy’s Platemys sulcatus. 
In the April (1869) number of the American Naturalist, Cope again mentions the name 
Taphrosphys, this time in connection with molops only, while to the new genus, Prochontas, 
were referred the species P. sulcatus, P. strenuus, and P. princeps. Of these again none had 
yet been described except P. sulcatus (Leidy). The latter therefore is the type both of 
Taphrosphys and Prochonias. Which of these names has precedence depends on which was 
issued first to the public, the April number of the American Naturalist or Cook’s Geology of 
New Jersey. Investigations not wholly satisfactory seem to show that the latter was first 
publisht, probably some time about the first of March, 1869. This conclusion enables us to 
