EMYDID.S. 357 



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 30 mm. The extreme width of 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, 35 mm. high, and it has a maximum thickness of 7 mm. The upper surface is con- 

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

 jagged suture with the contiguous ends of 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 of 10 mm. The anterior end of the first 

 vertebral has a width of 37 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 of 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 first 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 ot the first marginal scute the ndges diverge at an angle 

 with the midline and are interrupted by grooves parallel with the midlme. The distal halt ot 

 the third costal is markt by ridges running downward and obliquely toward one edge of 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. The middle 

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

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



On 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 furrows. 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 ndges 

 / that run downward and backward. 



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

 FIG. 454. Pseudemys cxlata. Left wi(lth was ^ mm j ts f ree border is subacute. On the 



Ib'ofVT' SU " faC U S P N St M' upp . el ' S ' de f the Hp the horn - coveied area extends backward 



a distance of 15 mm. Where 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 ot 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 hypoxiphiplastral suture. 



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

 nearly parallel with the gulo-humeral sulcus. The 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. 



Fig. 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 ' . scnpta and T. elegans in the form of 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 of the bone. P. concinna has narrower nuchal and first vertebral 

 scutes. The same is true of P. rubriventns. 



