i< \iYinn.i . 



sy< 



at the costo-vertebral sulcus, The third left peripheral (fig. 3) has a length of 32 mm. along 

 the free border, and a height of ^o mm. The extreme width oi the face which joins the second 

 peripheral is 20 mm. 



Fig. 4 of the plate cited illustrates the tenth left peripheral. It is 21 mm. along the acute 

 free edge, ^5 mm. high, and it has a maximum thickness ot 7 mm. The upper surface is con- 

 cave up and down ami slightly convex fore and att. It does not appear to have formed a 

 jagged suture with the contiguous ends ot the costals. 



The dimensions of some ot the scute areas can be only approximately determined. The 

 nuchal scute has a length of 17 mm. and a width ot io mm. The anterior end of the Hist 

 vertebral has a width of 57 mm. The anterior end of the fourth vertebral scute overlapt the 

 fifth costal bone a distance of 17 mm. Its width was therefore 34 mm. plus the as yet unknown 

 width ot the neural, amounting to probably 45 mm. 



The sculpture of the carapace may now be briefly described. On the nuchal bone the area 

 occupied by the Hist vertebral scute is ornamented with longitudinal ridges, 5 in a line 10 mm. 

 long. These ridges are more or less interrupted by the grooves concentric with the anterior 

 border of the scute. On the area of the first marginal scute the ridges diverge at an angle 

 with the midline and are interrupted hv grooves parallel with the midline. The distal half of 

 the third costal is markt by ridges running downward and obliquely toward one edge ot the 

 bone. These again are crost by ridges parallel with the distal end of the bone. The fifth 

 costal is similarly sculptured on the distal end, but the ridges are more irregular. 1 he middle 

 third has, along the anterior border, some strong ridges and grooves at right angles with the 

 sutural border, while the hinder halt is occupied by conical elevations having little regularity. 



< )n the third peripheral bone the area above the costo- 

 marginal sulcus is markt by ridges running downward; 

 the area in front of the intermarginal sulcus shows strong 

 ridges and grooves directed forward; while the area behind 

 this sulcus presents narrower and closer ridges, broken by 

 cross furrow's. The hinder peripherals have the area in front 

 of the descending sulcus markt by both vertical and hori- 

 zontal ridges; while the posterior half presents coarse ridges 

 that run downward and backward. 



The plastron possest an anterior lip (fig. 454) whose 

 width was 54 mm. Its free border is subacute. On the 

 upper side of the lip the horn-covered area extends backward 

 a distance of 15 mm. \\ here the bone joined the entoplastron 

 the thickness is 10 mm. The gular scutes overlapt the entoplastron. 



The hypoplastron (plate 57, fig. 5 ) is 72 mm. long, and it had a width of 55 mm. at the 

 inguinal notch. At the midline, near the anterior end, the bone is 13 mm. thick. The free 

 border of the bone is acute. The horn-covered band on the upper surface is 22 mm. wide at 

 the hvpoxiphiplastral suture. 



The area occupied by the gular scutes is ornamented with ridges and grooves which are 

 nearly parallel with the gulo-humeral sulcus. 1 he markings on the area of the humeral scute 

 are indistinct. The hypoplastron is distinctly sculptured. On the area of the abdominal scute 

 are short vermicular ridges, reminding one of the carapace of a trionychid. On most of the 

 area of the femoral scutes the sculpture suggests a tiled roof; but on the outer half there 

 are distinct longitudinal ridges, 7 of them in a line 10 mm. long. 



Fi\ 6 of plate 57 shows the left first costal of a smaller individual. It is markt by radiating 

 and concentric grooves and ridges. On the inner surface is an excavation for the inguinal 

 buttress. This buttress rose about 15 mm. above the lower border of the bone. 



This species differs from the living T . t< ripta and T . elegans in the form ot the nuchal bone 

 and the scutes overlapping it and in having had no notches in the borders of the carapace. 

 The nuchal here described has a good deal of resemblance to that on which Pseudemys 

 extincta is based. The latter nuchal is that of a considerably larger specimen and is much 

 smoother, the sculptural ridges having much less elevation. The nuchal scute, too, is longer 

 relatively to the length ot the bone. P. concinna has narrower nuchal and first vertebral 

 scutes. The same is true of P. rubriventris. 



10. 454. l'ii uJ, in ys calala. Left 

 half of lower surface of plastral 

 lip of type. Xf. U. S. N. M. 



