490 FOSSIL TURTLES OF NORTH AMERICA. 
The sculpture of the carapace is best displayed toward the free borders. It consists of 
abruptly sunken pits, of which there are usually 5 in a line 20 mm. long. Closer to the free 
borders the pits are smaller. Nowhere does there appear any tendency. for the formation of 
(PPO SSS we A a ote a ee eR eS ‘ straight rows of pits, such as 
! \ are seen on the costals of 
Amyda cartosa, of the New 
Mexico Wasatch. On the por- 
yee : tions of the carapace near the 
en H midline the pits are less con- 
iY spicuous. They appear to be 
/ as large, but the walls appear 
/ worn down. 
za The hypoplastron (fig. 650) 
is thick and heavy. At the 
suture with the hyoplastron, 
not far from the midline, the 
thickness is 13 mm. One border of the notch for the process of the xiphiplastron remains. 
This bone was articulated with the hypoplastron by a jagged suture and it must have extended 
anteriorly near the midline. The outer end of the hypoplastron, near the bases of the lateral 
processes, is 16 mm. thick. 
Evidently nearly the whole lower surface of the plastron was covered by the sculptured 
layer. The pits are smaller than those of the carapace, there being about 7 pits in a line 20 mm. 
long. Many of them coalesce to form winding furrows. 
This species differs from 4. fontanus 1 in having a narrower nuchal, much thicker bones, 
and a considerably coarser sculpture. It is referred to As spideretes provisionally. 
1 
1 
Fic. 650.—Aspideretes austerus. X 3. Right hypoplastron of type. 
Aspideretes vorax sp. nov. 
Text-fig. 651. 
This species was collected from the Laramie deposits near Ojo Alamo, San Juan County, 
New Mexico, in 1904, by Mr. Barnum Brown. The type is in the American Museum of Nat- 
ural History and has the catalog number 6140. The species is represented, as far as known, 
by only the nuchal bone; but this is complete. The length of the bone, from side to side, is 
200 mm. in a straight line, 215 mm. over the curve. The lateral conv exity 1s considerable and 
appears to have Bean somewhat greater than that of either 4. austerus or A. fontanus, both 
from the same locality as this species. The width at the midline is 45 mm., the greatest width, 
55 mm. The greatest thickness is 
15mm. There is a moderate median 
sinus in the anterior border. This 
border is not clipt off at a nearly 
right angle with the upper surface as 
“< Zz in the two other species mentioned 
Sa ae ee above; but is beveled down on the 
upper surface of the bone to a sharp 
edge. This beveled surface is not 
sculptured. The hinder border of the bone presents a median excavation, for the preneural 
bone. The latter bone was evidently unusually broad, the excavation having a width of at 
least 55 mm. The preneural border is thicker than that of 4. jontanus, the thickness 
being 7 mm. 
The sculpture of the bone is obscured by a layer of hard matrix; but so far as can be 
determined, it was intermediate between J. fontanus and A. austerus, approaching more 
closely the latter. 
Certain fragments of costals present probably belong to this species, but possibly to 4. 
jontanus. One of these, apparently the right sixth, is 35 mm. wide at the neural border, 
30 mm. wide more distally, and has a thickness of 8 mm. 
This species differs from 4. fontanus in having the free anterior border of the nuchal 
beveled, the bone thicker at the preneural border, and a coarser sculpture. From 4, austerus 
i ae Wales ace 
Fic. 651.—Asprderetes vorax. <3. Nuchal bone of type. 
