. Carnegie Institution of Washington publication. 498 FOSSIL TURTLES OF NORTH AMERICA. Neural. Median length. Greatest width. l 34 25 2 37 24 3 33 *3 4 3* 22 5 3° 16 6 20 9 The first neural is hexagonal with the long sides parallel. The second, third, fourth and fifth neurals are coffin-shaped; the sixth neural is pentagonal and pointed behind. The table here- with gives the dimensions of the neurals. The nuchal is firmly joined by its whole posterior border to the first costal plates and to the preneural. Its antero-posterior length is 38 mm.; its width from side to side is close to 154 mm. I
. Carnegie Institution of Washington publication. 498 FOSSIL TURTLES OF NORTH AMERICA. Neural. Median length. Greatest width. l 34 25 2 37 24 3 33 *3 4 3* 22 5 3° 16 6 20 9 The first neural is hexagonal with the long sides parallel. The second, third, fourth and fifth neurals are coffin-shaped; the sixth neural is pentagonal and pointed behind. The table here- with gives the dimensions of the neurals. The nuchal is firmly joined by its whole posterior border to the first costal plates and to the preneural. Its antero-posterior length is 38 mm.; its width from side to side is close to 154 mm. 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. puercensis. 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 ot 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 ot the shell of T. 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 convex surface, while that of P. sagatus has the bevel abrupt an
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