190 THe Ottawa NATURALIST. [January | 
that probably belong to this species are, a poorly preserved cara- 
pace (Cat. No. 1302) that has not been crushed nor distorted in any 
way and tlat therefore gives the natural convexity* of the upper 
surface, the right central part of another plastron (Cat. No. 1634), 
and the corresponding left portion of a fourth plastron (Cat. No. 
1633) of a size somewhat larger than the others and of greater 
shell thickness. 
The type of the Belly River species now described as new, 
under the above name, in the following paragraphs consists of the 
plastron (briefly described in 1902) with the front half of the cara- 
pace of one individual. Additional information ts given relative to 
the plastron but the characters of the carapace are now published 
for the firsttime. __ . 
The carapace is flattened and therefore appears unnaturally 
broad although the front margin may still be considered to be 
broadly rounded. On the left side the first five costal plates are 
preserved, on the opposite side the 1st, 2nd and 3rd remain. In 
the median line are the 1st, 2nd and 3rd neural plates. The nuchal 
plate is succeeded on the right by the first six marginal plates, on — 
the left by the first seven marginals of which the 3rd to the 7th are 
seen distinctly only in the lower aspect of the shell as they are 
injured above and are to some extent crushed under the distal ends 
of the costal plates. In plate III, figure 4, the carapace is shewn as 
seen from above, the epidermal shields being indicated by heavy 
lines and the sutures between the plates by faint ones. Marginal 1 is 
small and triangular in shape, but the succeeding ones present no 
unusual characters. The neurals are broader in front than behind 
and vary somewhat in outline. The 2nd and 3rd are roughly six- 
sided, the 2nd is nearly as long as broad, but the 3rd is con- 
siderably lengthened. The ist neural is much broader in tront 
than behind. It is of particular interest in that it is divided trans- 
versely, the division taking place well forward so as to separate it 
unequally into a short, broad front portion which is received into 
a concave emargination of the posterior border of the nuchal plate, 
and a hinder part that mainly separates the pair of 1st costals. 
*In this carapace the height of the centre of the upper surface above the 
plane of the margin is about 50 mm. 
