CHELONIIDA. 212 
obtuse, and along the hinder third is somewhat dentated. Anteriorly, the upper surface is 
furnisht with ridges which are sharp and prominent as they approach the free inner border, 
but which become obsolete in the opposite direction. These ridges seem to diverge from the 
anterior buttress of the hyoplastron (fig. 270, C), if such 
existed. At the anterior end of the bone the inner border 
turns slightly outward and, at an angle of about 75°, meets 
the sutural border for articulation with the epiplastron (fig. 
270, Ato B). These bones were not joined by squamosal 
suture, as they are in the Cheloniide and the Chelydridz, 
but by dentated suture. The lower surface of the bone is 
smooth and convex, especially transversely. The upper 
surface is concave. At the anterior end of the bone, on 
the upper surface, 190 mm. behind the anterior end (fig. 
270, C), is a slight elevation, as if it were the base of an 
axillary buttress. The lower surface of the bone just behind 
this point also indicates that the plastron rose toward the 
carapace, 
The portion of hypoplastron has a length of 155 mm. 
and a width of 125mm. Anteriorly the suture for the hyo- 
plastron is missing. The inner border is subacute and 
smooth, thus differing from the corresponding border of the 
hyoplastron. The suture for the xiphiplastron runs at right 
angles with the midline. It shows that the two bones were 
firmly united by coarse interdigitating teeth. ‘Toward the 
outer border the bone has a thickness of about 13 mm., 
but this diminishes slowly toward the inner border. As the 
outer border is approacht, the bone begins to ascend in a 
decided manner, as if approaching the carapace (fig. 270, 
D). If this conclusion is correct, as indicated by both hyo- 
plastron and hypoplastron, these bones were, relatively to 
their length, very narrow; and there is indicated a wide fonta- 
Fic. 270.—Lembonax polemicus. nel, that extended from the entoplastron to the xiphiplastra. 
Portion of plastron. Type. 4. It seems improbable that the inner borders came into close 
No. 1134 A.M.N. H. proximity. There were certainly no digitations extending 
Mice pecdecior arietlation with the epi: from the hyoplastron and hypoplastron toward the mid- 
plastron; C, base of axillary buttress; line, as there are in the Cheloniide and the Chelydride. 
D, probable base of inguinal buttress; A fragment of bone present indicates that the hyohypo- 
a ice eas ke MIDRPIAT On: plastral suture was formed by the interdigitation of finer 
processes than that of the hypoxiphiplastral suture. On the anterior end of the fragment of 
hypoplastron there are traces of this suture, so that this bone appears to have had a fore- 
and-aft extent of about 170 mm. : — 
The fragment of scapula present was that of a very large turtle. It is possible that it did 
not belong to the same individual as the plastral bones. The long diameter of the neck of 
the bone is g8 mm.; the short diameter, 42 mm. 
Lembonax? insularis Cope. 
Fig. 271. 
Lembonax insularis, Cope, Proc. Acad. Nat. Sci. Phila. 1872, p. 16.—Hay, Bibliog. and Cat. Foss. 
Vert. N. A., 1902, p. 444. 
Professor Cope’s materials representing this species were meager and his descriptions of 
it unsatisfactory. Nor have the means for increasing our knowledge of it been augmented; 
they have even been reduced. In the American Museum of Natural History there is a lot of 
bones labeled by Cope as the type of his Lembonax insularts, and bearing the museum's 
number 2347. This lot came to Cope from the Eocene bed of greensand at best evan 
Burlington County, New Jersey. Cope stated that the species was based on nuchal anc 
