TRIONYCHID. 487 
Fauna from the Judith River and Great Lignite Formations of Nebraska,” publisht as cited 
above. These parts, now preserved in the Academy of Natural Science at Philadelphia, 
must be regarded as the types of the species. A fragment of the right last costal plate, found 
near Long Lake, was identified, with some doubt, as belonging to the same species, and 
furnisht fig. 3 of Leidy’s plate above cited. This specimen is now 1n the National Museum at 
Washington and bears the catalog number 990. 
As regards the type specimens, there seems to be no certainty that the costal plate and the 
fragments of plastron were found associated. We must, however, for the present, assume 
that they belong to the same species. Should future discoveries prove that two species are 
involved, we shall have to take the costal plate as the type. 
This costal is 22 mm. wide, 5 mm. thick at the sutural margins, and 7 mm. thick thru 
the rib. The ornamentation consists of pits of varying size and shape separated by ridges 
whose summits are usually flat. There 
ee ce are, in general, 5 pits in a line 10 mm. 
ne a long. The pits are, as stated by Leidy, 
Q. . smaller at the proximal end of the costal 
than further outward; but this increase 
in size is due to the narrowing of the 
separating walls, not to a reduction in 
the number of pits in a given line. The 
pits are concave, and give the impression 
of having been scoopt by an engraver 
in a level surface. Near the sutural mar- 
gins of the costal the pits are almost 
wholly wanting and the surface is level 
and smooth. 
The fragments of the plastron of the 
type are 8 mm. thick. The lower surface 
is covered with short vermiculated ridges, 
some of which inosculate with the neigh- 
boring ridges while others do not. 
Scattered among these are small dot-like 
elevations. 
Mr. L. M. Lambe, of the Geological 
Surwey of Canada, described, as cited in 
the synonymy above, a nearly complete 
apace eae eS OBERT eronvnds Ne Senate es carapace and some plastral bones which 
the costal bones; pre, preneural; 7.1, 7. 6, the neurals; nu. p, : 
nuchal bone. he refers to this species. These he 
secured in the Belly River deposits, on 
the Red Deer River, in Alberta, British America. The nuchal bone is missing from the cara- 
pace. The length of the carapace (plate 89, fig. 15 text-fig. 643) as found, is 163 mm. The 
width of the nuchal has been estimated by Lambe as 5 mm. but it is probable that the 
width fore and aft was considerably greater. The maximum width of the carapace is 214 mm. 
The rear is broadly rounded, and the upper surface is moderately 
convex. There are present a preneural, 6 neurals, and 8 pairs of 
costals. The genus 4 spideretes is therefore indicated. 
Fic. 643.—Aspideretes foveatus. Carapace. X¥. 
Figure by L. M. Lambe. 
ee 
Neurals. | Length. Greates 
| width. > : ‘ 5 
| The preneural is short, being 18 mm. wide and 12 mm. long. 
The 4 anterior neurals are broader behind than in front; the 
: res fifth is a parallelogram; the sixth is broad in front and pointed 
, a 14 behind. The dimensions of the neurals are given in the table. 
4 21 13 The eighth costals are small, almost vestigial, as in some 
8 | ‘ . A : 
| 5 : oA species of Platypeltis, the lateral extent of one being about 22 
6 16 14 \ E 5 
mm.; of the other, 20 mm. Each lies in a notch in the costal in 
front of it, and they do not come into contact at the midline, the 
latter condition being probably an individual peculiarity. The sculpture resembles closely that 
of Leidy’s type. It is thus described by Lambe: 
