. Carnegie Institution of Washington publication. :. 49 I The total length in the midline is 538 mm.; the greatest width, 665 mm. The greatest height of the center of the carapace above the distal ends of the costals is only about JO mm., but in life the height may have been somewhat greater. The nuchal has an antero-posterior extent ot 75 mm., and an extent from side to side of 400 mm. There was probably a preneural bone, but this region is damaged so that the presence ot the bone is uncertain. It it was not developt, the first neural must have been very large. Furthermore, there
. Carnegie Institution of Washington publication. :. 49 I The total length in the midline is 538 mm.; the greatest width, 665 mm. The greatest height of the center of the carapace above the distal ends of the costals is only about JO mm., but in life the height may have been somewhat greater. The nuchal has an antero-posterior extent ot 75 mm., and an extent from side to side of 400 mm. There was probably a preneural bone, but this region is damaged so that the presence ot the bone is uncertain. It it was not developt, the first neural must have been very large. Furthermore, there are some appearances in the region in question which indicate that there was a preneural. The probable condition in this part of the carapace is indicated in the text-figure (fig. 646). In the carapace, as restored, there seems to be a suture between the inner anterior angle of the first left costal and a pre- neural; but the supposed suture may be merely a fracture. There is also a fragment ot bone which appears to be a portion of the preneural and a portion of the first neural, but it is un- certain whether or not the fragment belongs where it is placed. If present, the preneural was probably wider at its anterior end than at the posterior. On the other hand, a very large first neural, like that of Amyda egregia, may have occupied the entire space between the first costals. The evident relationship of this species to As pideretes coalescens Cope, as figured by Lambe under the name Trionyx vagans, renders the presence ot the preneural more probable. Behind the preneural there were 7 neurals. These had the usual coffin-shape, with the nar- rower ends directed forward, except the sixth, which is oval in form, and the seventh, which has the broader end in front. The neurals mostly decrease in size from the first to the last. The table below gives the dimensions of the pre- neural and the neurals. The first, seventh, and eighth costals are considerably broader at their proximal, t
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