184 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 83 



forward margin. It measures 204 mm from end to end in a straight 

 line and 210 mm over the curve. The same dimensions of the type 

 nuchal are 200 and 215 mm, respectively. The width at the mid line 

 is 45 mm, the same as in the type. Its greatest thickness is 14.5 mm, 

 whereas the type has a thickness of 15 mm. The anterior border is 

 steeply beveled to a sharp edge; this beveled surface without sculp- 

 turing is traversed by a faint median sinus. The posterior border is 

 hollowed out at the center for the articulation of the preneural. 

 This excavation has a width of about 38 mm. 



This turtle is a large one, having a transverse diameter at the 

 suture between the third and fourth costals of 482 mm. The outer 



Figure 1G. — Carapace of Aspideretes vorax Hay. U.S.N.iSI. uo. 

 12988. nv. Nuchal ; pn, preneural ; nl and 7i3, neurals 1 and 

 3, respectively. One-sixth natural size. 



end of the first costal contributes to the formation of the anterior 

 and lateral borders of the shell, as shown in figure 16. It has a 

 greatest width of 82 mm ; the second and third each measure 66 mm 

 across their outer ends. The outer ends of the costals are beveled off 

 to a sharp lower edge. This edge is without sculpture. Through the 

 rib the costals have a thickness at their outer ends of 15 mm, at the 

 proximal end 8 mm. 



The preneural is quadrangular, being slightly wider than long. 

 Anteroposteriorly it measures 38 mm. The neurals are of the usual 

 coffin shape ; the first is 38 mm long, the second 51 mm. 



The sculpture of the carapace consists of a network of round- 

 topped ridges surrounding shallow pits. On the outer halves of 

 the costals they tend to arrange themselves in rows running parallel 

 with the adjacent border of the carapace. On the nuchal and the 

 proximal portions of the costals the pits are irregular but evenly 

 distributed. On the neural surfaces and in places on the upper ends 

 of the costal, they are sparsely distributed, in some spots smooth and 

 devoid of ornamentation. The costals have a narrow band along the 

 intercostal sutures formed by a series of low ridges set at right angles 

 to the suture. 



