164 



specimen, corresponding with the position of whal appears to be the outer 



poll ion of the nuchal scute area. The latter apparently is of great width, at 

 least an inch at its conjunction with the first vertebral scute area. 



The latter and the last of the series are prominent in the median line, where 

 they form a thick, rounded ridge. A low interrupted ridge extends along the 

 median line of the carapace, which is barely evident in the first-described 

 specimen. The short divisions of the ridge are flanked by equally long fusi- 

 form elevations slightly divergent forward. In addition, the carapace is 

 rather irregularly prominent along the position of the lateral grooves of the 

 vertebral scute areas. The intermediate vertebral scute areas are proportion- 

 ately narrower than in the first specimen. The second and third are slightly 

 longer than wide; the fourth a little wider than long; and the first and last 

 in width considerably exceed the length. 



The plastron is preserved nearly complete, and is represented in Fig. 3, 

 Plate XIII. It appears as if originally it had been less flat than in the former 

 specimen, as, independently of fractures, it turns up more at the extremities 

 as well as at the bridges. 



The anterior extremity, which is lost in the former specimen, affords an 

 opportunity of completing our knowledge of the plastron. It is shorter and 

 narrower than the posterior extremity, but is nearly like it in shape. The free 

 border' is obtusely rounded, and is slightly more thickened and prominent at the 

 divisions produced by the scute impressions. These do not mark the upper sur- 

 face as in the Emydse. The lower surface exhibits one of the most remarkable 

 peculiarities of the genus, which is the possession of two pairs of gular scutes. 



The first pair of gular scutes are comparatively small, and are defined poste- 

 riorly, in the usual manner, by oblique grooves diverging at an angle of 45°. 



The second pair of gular scute impressions escaped my notice until I had 

 seen several additional specimens. As this did not occur until after the draw- 

 ing of Fig. 3 was made, they are not there represented. They are seen in 

 Fig. 1, Plate XV, which was subsequently and more accurately drawn from 

 the same specimen. They are rather larger than the first pair, and are 

 defined posteriorly by a serpentine groove directed outwardly nearly from the 

 same point as the grooves in advance. 



The remaining scute areas of the plastron arc nearly like those of the pre- 

 ceding specimen, except those covering the pedicles. 



Only three scutes covered the latter in the second specimen, the one cor- 

 responding with the first submarginal scute area of the first specimen being 



