= 
PLASTOMENID#. 471 
1110 and 1113, the specimens appearing on Cope’s plate xxvi having the latter number. 
Professor Cope states (Syst. Cat., p. 35) that 4 individuals were represented in his collection. 
All these, if Ub present, are included under the catalog numbers just given. The originals 
of Cope’s figs. 1, 2, and 3, of his plate xxvi, were considered by him to constitute the type of 
the species, aad are said to belong to a single individual. Fig. I represents the outer end of 
the left hypoplastron; hg. 2, apparently a “fragment of the left hypoplastron at the bridge; 
while Cope’s fig. 3 1s the distal end of a Gaal In Cope’s fig. 2 the left side represents the 
sutural border for articulation with the hyoplastron, and the concave edge on the upper right- 
hand side is the inguinal notch, which is here quite acute. If this identification of the bone is 
correct, the notch was more abruptly formed than is usual in species of Trionychide, and 
quite as abruptly as in Plastomenus thomas:. In order to understand the relations of the bones 
represented by the two figures, fg. 2 must be conceived as being removed to the left of fig. 
in such a way that the left edge, the sutural one, shall be turned go degrees and placed about 
parallel with the upper border of fig. 1. When the two figures are thus placed, there should be 
perhaps about 35 mm. of space between their lower borders. Fig. 630 represents these bones 
in the position suggested. 
The fragment of costal plate represented by Cope’s fig. 3, plate xxvi, has a thickness of 
10mm. The figure is reproduced (plate 86, fig. 2). The upper surface is beveled off some- 
what and the upper layer of bone oy erhangs the deeper 
layers. The upper surface of the bone is sculptured with 
Pee narrow ridges which run parallel with the free border of 
= the costal. Between these sharp ridges are furrows, 
which are occasionally divided into pits by intersecting 
ridges. There are 4 of these furrows in a distance ae 
10 mm. QOne tragment of the upper end of a costal is 
found with the type. It shows the rib-head and was 
originally about 20 mm. wide. ‘The thickness at the 
Combination of two of Cope’s fig- Satara border is 6 mm.; thru the rib it is 7 mm. The 
ures to show their relative positions. angle between the articular border for the cor eee 
x4. No. 1113 U.S.N.M. Type. neural and that for the outer hinder angle of the neural 
next in front shows that the neurals were much wider 
behind than in front. The upper 25 mm. of the upper surface is covered with large irreg- 
ular pits, about 3 in 10 mm. Distally they become smaller. It is possible that this fragment 
does not belong to this species, but other fragments appear to form the transition to the 
original of Cope’s fig. 3, plate xxvi. 
The fragments which belonged to Cope’s third specimen, and which furnisht figs. 27 to 31 
of his plate xxv, belonged to a larger animal. It is possible, too, that they belonged to a 
distinct species. As in the type, the costal is thickened distally and the sculpture consists of 
ridges crossing the costal and connected at intervals by intersecting ridges. In the type of the 
species the ridges are of nearly uniform size or perhaps they increase slightly in breadth and 
distance apart toward the free margin of the costal. In the third specimen, however, they are 
broader and more obtuse and they become distinctly narrower and more crowded toward 
the margin, as is shown in Cope’s figures. Furthermore, the sculptured layer of the type 
overhangs the deeper layers, at the fee margin, more than it does in the originals of Cope’s 
figs. 29-31. All these differences may, however, be due to variations in age and size or to 
varying positions in the carapace. 
In the lot of bones representing this species there is a portion of a plastron, apparently a 
part of the left hypoplastron from the inguinal region, and hence corresponding to the piece 
represented by Cope’s fig. 2, plate xxvi. This presents a sculpture in which the ridges run at 
right angles with the hyohypoplastral suture. At this suture the thickness is 8 mm., but nearer 
the free border it is 15 mm. An outer extremity of a hypoplastron in the lot shows a sculpture 
different from that of the type individual, and more like that of 4myda ventricosa. 
More and much better materials are needed in order to determine the structure and 
relationships of this tortoise. The form of the hypoplastron of the type and to some extent 
the sculpture of the carapace seem to indicate that the species belongs to, or is near, the genus 
Plastomenus. 
Fic. 630.—Plastomenus le ptomttus. 
