498 FOSSIL TURTLES OF NORTH AMERICA. 
The first neural is hexagonal with the long sides parallel. The 
Neural, | Median | Greatest second, third, fourth and fifth neurals are cofin-shaped; the 
ere aay sixth neural is pentagonal and pointed behind. The table here- 
i with gives the dimensions of the neurals. 
; 34 5 The nuchal is firmly joined by its whole posterior border to 
5 s a the first costal plates and to the preneural. Its antero-posterior 
4 32 22 length is 38 mm.; its width from side to side is close to 154. mm. 
5 . : Its whole upper surface, with the exception of the beveled edge, 
is covered with the ridges and pits of the ornamentation. It is 
therefore in form, in extent of articulation, and ornamentation 
extremely different from the nuchal of T. puercensts. 
The eighth pair of costals together form about 125 mm. of the hinder margin; fore and 
aft in the middle line they measure 38 mm. 
The sculpture (plate 93, figs. 2, 3) consists of a coarse network of ridges which inosculate 
somewhat irregularly and inclose deep pits of varying sizes. 
The sculpture is coarsest on the distal third of the costal 
< plates, where there are about 5 pits in a line 25 mm. long; 
and here there is a tendency toward an arrangement of the 
stronger ridges across the costal plates. Nearer the midline 
of the shell there will be found about 6 or 7 pits in this distance. 
Near the free margins of the costal plates there is a tendency 
for the ridges to break up into tubercles having elongated or 
circular bases. It might be difficult in some cases to distin- 
guish fragments of the shell of J. puercensis bearing its coarser 
sculpture, from fragments of the present species bearing the 
finer ornamentation. If they are marginal pieces the species 
may be determined usually from the fact that the margin of 
. _ P. puercensis is beveled off less abruptly and with a plane or 
Se convex surface, while that of P. sagatus has the bevel abrupt 
ond ae oe and often slightly concave. 
ae ; This species resembles in many ways those figured by 
Professor Cope on plate xxvi of his Extinct Weitebrara 
obtained in New Mexico (Wheeler Survey West 100th Merid- 
ian, vol. 1v). 4. sagatus, however, differs from T. le ptomitus 
and 7. cariosus in not having the sculptured layer of bone 
overhanging the supporting layers at the outer ends of the 
costal plates; likewise, in not having the ridges of the sculpture arranged i in lines parallel with 
the length of the shell. 
Hic 652.—Aspideretes sagatus. 
Carapace of type. X $. 
Aspideretes? nassau sp. nov. 
Text-fig. 653. 
The only known specimen of this species was collected by Dr. Marcus S. Farr, of Princeton 
University, Princeton, New Jersey, in Fort Union deposits, at Duffy’s ranch, 18 miles from 
Melville, Sweet Grass County, Montana. The specimen belongs to the university named. 
Only the carapace (fg. 653) is represented. 
‘The nuchal one) all of both first costals except a small part of the one of the right side, 
and the first and second neurals are missing. It is assumed that this species, like cose from 
the approximately equivalent Puerco deposits, possest a preneural bone and belonged, there- 
fore, to the genus Aspideretes. There were certainly 8 pairs of costals and 7 eneaies 
The fadividual here described was evidently an aged one, since the disk oe out to 
the ends of the ribs. The species was a small one. The length can not be exactly determined, 
but was approximately 195 mm. The width, in a straight line, is 200 mm. The rear of the 
carapace is truncated, more exactly, slightly concave in outline. The upper surface is convex 
from front to back, more strongly so from side to side. The free borders are cut off nearly 
perpendicularly to the upper surface and are about g mm. thick. Toward their proximal ends 
the costals are reduced in thickness to 5 mm. 
