130 FOSSIL TURTLES OF NORTH AMERICA. 
of the fifth costal at the distal end is 77 mm. At the costo-vertebral sulcus the seventh and 
eighth costals (fig. 149) are each 39 mm. wide. The eighth is 47 mm. wide at the distal end. 
On the inferior side of the eighth costal is seen the base of the small rib-head. Behind this is 
the co-ossified end of the vestigial tenth rib. 
The surface of the bones of the carapace is almost everywhere more or less uneven. On 
the nuchal and the anterior peripherals the areas occupied by the scutes are tumid, and the 
sulci run in deep and broad valleys. The same remarks apply to the dorsal region of the 
carapace, so far as represented. The sulci of the distal portions of the costals and of the hinder 
peripherals are deeply imprest. 
_ VS \ The upper surfaces of the hinder 
y 3 \ peripherals are more or less undu- 
: i y \ y lating. 
148, é we The nuchal scute (fig. 147) is 
\ smaller than that of either O. 
_— —- emarginatus or O. gibb1; its width 
, ; av anteriorly being 47 mm.;_poste- 
ops i riorly, 80 mm.; its fore-and-aft 
YO Sa 7 A extent, 24 mm. The first marginal 
per.9 \ er, is 62 mm. along the front; 30 mm. 
5 A where it joins the nuchal; 45 mm. 
Sg where it joins the second marginal. 
\ On the tenth peripheral the costo- 
pe — marginal sulcus runs 30 mm. 
: } below the upper border of the 
eas 150. bone. At the midline behind, the 
\ 4A cra sulcus crosses on the hinder supra- 
< / | a pygal. 
ee peti ; \ The anterior vertebral scute 
had a width of about 200 mm. 
py ‘’ On the fourth costal the costo- 
{ 
perso 
ee nN J vertebral sulcus crosses the bone 
ees tL ; at a distance of about 44 mm. 
eo. from the neural border.  Esti- 
ISI. : mating the width of the neural at 
Fics. 148-151.—Osteopygis robustus. Costals, peripherals, 45 mm. the width of the third ver- 
and pygal of type. tebral would be about 135 mm. 
148. Section at proximal end of first peripheral. 3. The fourth vertebral, at the ante- 
149. Right seventh and eighth costals, hinder peripherals, and pygal. x4. rior border of the seventh costal, 
150. Section of anterior end of tenth peripheral. xh. to have b 5 
151. Section along middle of pygal. 4. ep pests YEN WS och Ue inete) 
mm. wide. That of O. g1bbi was 
about 135 mm. wide. The fifth vertebral had a width posteriorly of 190 mm. Its length was 
close to 155 mm. 
On account of the common feature of sutural union of all the peripherals with the costals, 
this species needs comparison only with O. emarginatus and O. gibb1, and such comparisons 
have already been made. 
Osteopygis chelydrinus Cope. 
Plate 23, figs. 4-7; plate 28, figs. 1-4; text-figs. 152-154. 
Osteopygis chelydrinus, Cope, Proc. Acad. Nat. Sci. Phila. 1868, p. 147 (nom. nud.); Geol. New Jersey, 
Cook, 1869, Append., p. 735 (nom. nud.); Amer. Naturalist, m1, 1869, p. 89; Ext. Batrach.. 
Reptilia, Aves N. A., 1869, pp. 135, 138, plate vii, fig. 8—Hay, Bibliog. and Cat. Foss. Vert. 
N. A., 1902, p. 441. 
Catapleura chelydrina, Corr, Vert. Cret. Form. West, 1875, p. 259. 
In his Synopsis of the Extinct Batrachia, Reptilia, and Aves of North America, Professor 
Cope stated that this species was represented by “‘only 10 marginal plates more or less perfect 
and some costals”; also that the species was referred to the genus Osteopygis because the 
