494 FOSSIL TURTLES OF NORTH AMERICA. 
Most of the costals are widened at their distal ends. The costals of the sixth pair join 
medially without interruption. Those of the eighth pair are directed backward, and join for 
their full length in the midline, their distal ends forming 
the median portion of the border of the shell. The free 
Element. Bengthen | Width: borders of the median costals are beveled off at an angle of 
about 45°; the more posterior ones are rounded on the edge. 
Preneural.... 274 23 The thickness in the middle of their length is usually 
ena 28 25 close to 6 mm. at the sutures, while thru the rib the thick- 
Neural 2 36 23 é 5 : 
Rreurales a 23 ness amounts to 8 mm. At their distal ends the thickness 
Neural 4 33 22 at the sutural edges is 10 mm. and thru the rib about 12 
Neural 5 28 15 : : i d . ss 
Roe 8 22 mm. The ribs are quite prominent on the under side of 
“| | the costal bones, and occupy about two-thirds of the width 
of the plate. Most of the bodies of the dorsal vertebra 
are eroded away, and there is exposed a cast of a portion of the neural cord about 5 mm. in 
diameter and 160 mm. long. 
The sculpture (plate 96, fig. 2) appears to agree well with that of the type of this species; 
but it has suffered somewhat from weathering. On the middle of the costals there are 4 or 5 
pits in 10 mm. On the neurals and the distal ends of the costals they are somewhat smaller; 
on the nuchal and in places on the hindermost pair of costals, somewhat larger. 
This specimen reveals to us the convexity of the carapace, as well as the form of the hinder 
border. 
Two carapaces have been submitted to me for examination, which had been collected by 
Prof. J. B. Hatcher in the Judith River beds on Fish Creek, Montana. These bear the 
numbers 445 and 541 of the Carnegie Museum, Pittsburg. No characters are observed which 
serve to distinguish these carapaces from that of the type of 4. beecherr. It is not improbable, 
however, that hey belong to a distinct species. 
Prof. O. C. Marsh, as cited in the synonymy, has reported Trionyx ; foveatus from the 
Ceratops beds near Denver, Colorado. The writer does not know on what the determination 
was based; but it appears probable that the specimens belonged to 4. beecher:. 
Aspideretes fontanus sp. nov. 
Text-fig. 648. 
From the Laramie beds at Ojo Alamo, San Juan County, New Mexico, Mr. Barnum 
Brown, of the American Museum of Natural History, in 1904, brought materials belonging 
apparently to 3 species of ine 
genus A spideretes. Of these the 
present is represented by nearly 
the whole of the right half of the 
nuchal and a conenernle part of 
the right first costal. The number 
of the specimen is 6070. 
At no point does this piece of 
‘ i ‘nuchal come to the midline; hence 
\ a Yo \ we can not determine the exact 
Seas _-~~ extent of the bone laterally. It 
; \ ce was, however, not far from 260 
’ | Beat mm. The animal was therefore 
: \ Soe one of considerable size. The 
Siete inner hinder angle of the bone 
' x presents a part of the sutural bor- 
der for the preneural, and from 
this to the outer end of the nuchal 
is 125 mm. Thewidth of the bone, 
where it came into contact with the preneural, is 60 mm. The anterior border is not beveled, 
but 1s cut off nearly at right angles with the upper surface. The greatest thickness, thru 
Fic. 648.—ds pideretes fontanus. Part of nuchal and part 
of first right costal of type. 
