. Carnegie Institution of Washington publication. i?b 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 sul
. Carnegie Institution of Washington publication. i?b 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. The upper surfaces of the hinder peripherals are more or less undu- lating. The nuchal scute (fig. 147) is smaller than that of either O. emarginatus or 0. gibbi; its width anteriorly being 47 mm.; poste- riorly, 80 mm.; its fore-and-aft extent, 24 mm. The first marginal is 62 mm. along the front; 30 mm. where it joins the nuchal; 45 mm. where it joins the second marginal. On the tenth peripheral the costo- marginal sulcus runs 30 mm. below the upper border of the bone. At the midline behind, the sulcus crosses on the hinder supra- pygal. The anterior vertebral scute had a width of about 200 mm. On the fourth costal the costo- vertebral sulcus crosses the bone at a distance of about 44 mm. from the neural border. Esti- mating the width of the neural at 45 mm. the width of the third ver- tebral would be about 135 mm. The fourth vertebral, at the ante- rior border of the seventh costal, appears to have been about 100 mm. wide. That of 0. gibbi 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 compari
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