524 FOSSIL TURTLES OF NORTH AMERICA. 
beyond the margin of the carapace about 30 mm. The thickness of the costals, measured at 
the sutures, is abate 8 mm.; measured thru the ribs it is about 13 mm. The costals of the 
seventh and the eighth pairs meet their fellows along the midline. Those of the eighth pair 
are rather small. 
The sculpture of the carapace is of median coarseness, there being about 3 pits in a line 
1o mm. long. The pits are shallow and the rounded walls surrounding them are about as 
wide as the pits. For some distance on each side of the midline the sculpture is nearly obsolete. 
The plastron (fg. 679) incloses large median fontanels. The entoplastron and the epi- 
plastra are slender bones, resembling those of Platypeltis spinifera. They possess no “‘cal- 
losities.”” Nearly the whole surface oF the hyoplastra and the hypoplastra is furnisht with pits 
and ridges, but these are not so coarse as those of the carapace, there being about five pits in a 
line 10 mm. long. These are better developt on the outer ends of the Bones mentioned. The 
median borders of these bones show a band consisting of a network of bony fibers. The 
surfaces of the xiphiplastra present a similar interlacement of bony fibers. 
The width of the bridge, where narrowest, is 51 mm., of which 26 mm. belong to the 
hypoplastron. The median border of this bone possesses about ten digitations, of which the 
two posterior are the largest and receive between them the inner process of the xiphiplastron. 
The xiphiplastra are slender bones. They join each other by means of anterior two-tootht 
processes and by broad posterior processes. 
The bones belonging to the vertebral column, the shoulder and pelvic girdles, and the 
limbs present no peculiarities. 
This species resembles in some respects Amyda uintaénsis L eidy. It differs, however, in 
being more elliptical in outline, in having the greatest width nearer the middle of the length, 
7 neurals instead of 6, a differently formed first neural, a sculpture finer and of different 
character, and a narrower plastral bridge, of which the hypoplastron is wider than the hyo- 
plastron. 
Dedicated to the writer’s daughter, Miss Frances Steele Hay. 
Amyda salebrosa sp. nov. 
Plate 104, fig. 1; text-fig. 680 
Amyda salebrosa 1s based on a specimen which was collected by Mr. Walter Granger at 
Dry Creek, i in southwestern Wyoming, June 30, 1904. The level at which it was found is (Ge 
the middle of the Bridger deposits. Only the carapace is present, but this is practically com- 
plete. It bears the number 3941 of the American Museum’s catalog. 
The carapace (plate 104, fig. 1; text-fg. 680) was broad and probably rather flat. The 
front margin is broadly rounded, the rear truncated. The length is 425 mm.; the greatest 
width, 455 mm. Considering the great size of the carapace, it is ‘rather thin, being only 8 mm. 
thick at the sutural borders, near one ends of the costals. Thru the ridges on fie underside 
of the carapace, produced by the mbs, the thickness is 12 mm. The outer ends of the costals 
are beveled off from above. 
The nuchal has a lateral extent of 267 mm., and a fore-and-aft extent of 57 mm. Its whole 
upper surface is pitted. Its outer ends overlap the outer anterior 
angles of the first costals. 
There are 7 neural plates, and these decrease in size from the 
first to the last. The accompanying table gives the dimensions. 
Neural. Length. Width. 
I 67 38 The first neural is hexagonal, with the short sides consisting 
z 55 » of the posterior and the two postero-lateral. The next two 
- re ys neurals have the narrow end directed forward; the fourth is 
5 37 21 nearly a parallelogram; the fifth and the sixth have the wider 
: oF ms end in front; the seventh is pentagonal. The costals of the 
| seventh pair join in the midline behind the seventh neural. 
Those of the eighth pair met along the midline for a distance of 
about 30 mm.; and each had a lateral extent of about 48 mm. The distal ends of the ribs pro- 
ject but little beyond the borders of the disk. In younger specimens they will doubtless be 
found to project a greater distance. 
