492 FOSSIL TURTLES OF NORTH AMERICA 
shell. Fig 8 represents the outer portion of the fourth left costal, the hgure being oriented as 
in fg. 7. Fig. g presents the sculpture on the proximal half of the third left costal, the upper 
end being toward the front of the animal. 
This species differs from 4. beecher: in being more deprest, in having a greater proportion- 
ate width, and in having a coarser and more irregular ornamentation. From Cope’s type of 
As pideretes? vagans it seems to differ in having a coarser sculpture. From 4. coalescens Cope, 
as exemplified by Lambe’s specimen described under the name of T. vagans, it differs in 
having the carapace convex in front and in the different form of the nuchal and in the relatively 
greater width; likewise, in possessing a greater number of neural plates and much larger 
eighth costals. 
Aspideretes beecheri Hay. 
Plate go, fig. 2; plate g2, figs. 1, 2; plate 96, figs. 1, 2; text-fig. 647. 
Trionyx foveatus, Baur, Proc. Acad. Nat. Sci. Phila. 1891, p. 418.— ?Marsu, Monogr. U. S. Geol. Surv. 
XXVIII, 1897, Pp. 527: 
As pideretes beechert, Hay, Amer. Jour. Sci. (4), XVII, 1904, p. 274, plate xvi; Amer. Geologist, xxxv, 
1905, p. 338. 
In the Marsh collection of fossil vertebrates at Yale University, there is a finely preserved 
specimen of a trionychid to which the above name is given. It was collected in the year 1889, 
by Prof. J. B. Hatcher and Dr. C. E. Beecher, in the Laramie beds of Converse County, 
Wyoming, on the east side of Lance Creek. It is named in honor of one of the collectors, 
Dr. C. E. Beecher, formerly professor of paleontology in Yale University. 
This specimen was studied by Dr. G. Baur and was identified by him as Trion yx yx jove atus 
of Leidy. The present writer does not agree with this identification. Leidy’s species was 
based on scant materials, but the ornamentation of the costal bones is characteristic and has 
led to the identification of the species by Mr. L. M. Lambe in well-preserved and complete 
remains. These remains indicate a very different trionychid from the one here described. 
The type of 4. beechert presents the limbs nearly complete, a portion of the neck, the tail, 
the shoulder and pelvic girdles, a large portion of the carapace, and the whole of the plastron. 
The skull, some costals, and most of the neurals are missing. 
The carapace (plate 92, fg. 1) was nearly as broad as long, the length being close to 323 
mm.; the width 310 mm. It was apparently rather convex, but has suffered some crushing 
during fossilization. The front of the shell, along the nuchal, was nearly straight, but at ihe 
ends of this bone the border has a scallop on ach side. The lateral borders are somewhat 
sinuous. The hinder border appears to have been excavated, but here the costals are wanting. 
The nuchal has a width of 30 mm. in the midline, being somewhat notcht for the reception 
of the preneural, Its outer sy appears to project slightly over the first costal plate. The 
preneural is of hexagonal form, 27 mm. long and 30 mm. wide. The first true neural is hexag- 
onal, with the narrow end forward, as usual in the species of this family. It has a length of 
32 mm. anda width of 21 mm. The second neural is of similar shape, 42 mm. long and 26 mm. 
wide. The costals display nothing characteristic. “There were probably 8 of fen. The ends 
of the costal ribs project beyond The disk about 17 mm. anteriorly, but posteriorly they are 
longer, that of the seventh being about 50 mm., fae of the eighth probably about 70 mm. 
The costals are about 5 mm. thick along their borders. 
The sculpture of the carapace consists of a network of ridges inclosing rather deep pits. 
Of these there are about § ina distance of 10 mm. Usually they are without definite arrange- 
ment, but toward the outer ends of the costals they dispose themselves in rows parallel with fhe 
margin of the shell. The bottoms of the pits are flat, and the walls rise abruptly. In Aspideretes 
joveatus the pits have concave bottoms and the surrounding walls rise gradually. Often, too, 
there are broad smooth spaces between the pits on the proximal ends of the costals of 4. 
foveatus. In A. beecher: the sutures between the costals resemble seams in leather sewed with 
fine stitches. 
The plastron is complete. The entoplastron is slightly notcht in front. Its lateral limbs 
include between them less than a right angle, and the length of each is 93 mm., measuring 
from the anterior notch of the body ‘of the i The epiplastra are broad at their anterior 
ends. They resemble much those of Platypeltrs mutica. The hyoplastra are not co-ossified 
