TRIONYCHID^. 



499 



The neurals are relatively broad. The accompanying table shows their dimensions. 



It is not certain that the outlines of 

 the seventh neural are correctly drawn in 

 the figure; but they appear to be as shown. 

 If so, this neural is of unusual form and size 

 for the posterior one. It did not wholly 

 separate the costals of the seventh pair at 

 the midline. 



The central portions of the upper sur- 

 face of the carapace are nearly smooth. 

 Gradually toward the outer borders a 

 sculpture appears. On a band about 35 

 mm. wide around the borders this sculp- 

 ture is quite distinct and consists of ridges 

 separated by furrows and pits. These 

 ridges run nearly parallel with the free bor- 

 ders of the carapace. The furrows are usually narrower than the flat-topped ridges. A line 

 10 mm. long crosses four of the ridges. 



Nassau, an old name for Princeton University. 



PIG. 653. Aspideretes nassau. Carapace of type. 

 Xo-35- Partly restored. 



Aspideretes puercensis sp. nov. 



Plate 94, figs. 1-3; plate 104, figs. ^, 3; text-figs. 654, 655. 



This species is represented by a single specimen, which belongs to the American Museum 

 of Natural History, and bears the number 1202. The right side of the carapace is nearly com- 

 plete, lacking only the eighth 

 costal and the free ends of 

 most of the ribs; and there 

 are present large portions of 

 the left side of the plastron. 

 All these parts belonged to a 

 single individual, which was 

 collected by Dr. J. W. Wort- 

 man and Mr. O. A. Peterson, 

 in 1892, in the Puerco beds 

 of New Mexico, probably in 

 the southern part of Rio 

 Arriba County. 



Up to the present time, no 

 species of Tnonychidae has 

 been described from the 



654. Carapace. 



655. Plastron. 



FIGS. 654 AND 655. Aspideretes 

 puercensis. X a- 



Puerco Eocene except Con- 

 chochelys admirabdis Hay. 

 Professor Cope has credited 

 (Proc. Amer. Philos. Soc., 

 XX, p. 461) to the Puerco deposits the Wasatch species Plastomenus communis, but it was 

 with a doubt, and the species was not included in later lists. Nor is it mentioned in Cope's 

 Vertebrata of the Tertiary Formations of the West as belonging to the Puerco. 



6 54 . 



