136 MEMOIRS OF THE CARNEGIE MUSEUM 



the nuchal border. The median portion is high and vaulted. The length of the 

 carapace is estimated to have been about 390 mm., its breadth is 286 mm., its height 

 at the center is 130 mm. The plastron is broad, and, like many other species of the 

 genus Echmatemys, there is but little space in front of the axillary notches for the 

 exit of the limbs. The margins of the carapace forward of the axillary notches 

 are thickened and rounded, but forward it thins rapidly, coming to an obtuse edge 

 along the median anterior border. The peripherals of this region do not flare up- 

 ward, though those immediately posterior to the inguinal notches show a tendency 

 to do so. 



The carapace is smooth, except that the median costal areas are crossed antero- 

 posteriorly by a series of wide, parallel, wavy, flattened ridges. In a line 12 mm. 

 long three of these ridges may be counted. This ornamentation is inconspicuous 

 unless the light strikes the surfaces at the proper angle. It is the obscure nature of 

 this ornamentation which has suggested the specific name. 



The nuchal plate is unusually long and narrow. At the point of its greatest 

 transverse diameter the sides are considerably within the boundaries of the first 

 vertebral. The length of the nuchal is 65 mm.; its greatest transverse diameter 

 is 51 mm. ; the free border measures 40 mm. The nuchal surface is without median 

 elevation. Echmatemys obscura is the only species of the genus which has the 

 nuchal plate longer than wide. 



All of the neurals posterior to the first are broadly hexagonal, and all posterior 

 to the first are broader than long. The second and third have the anterior end 

 concave, those posterior being straight. Their principal measurements are given 

 in the accompanying table. 



Dimensions of Neueals. 

 No. Length. Width. 



1 47 35 



2 38 40 



3 43 43e 



4 39 47 



5 31 41 



6 — 44 



e, estimated. 



The costals posterior to the first alternate in having the distal ends slightlj^ 

 wider and narrower than the proximal ends. 



The peripherals are moderately high, the first extending inward from the 

 border 50 mm., the seventh 58 mm.; the eighth 55 mm. The border above the 

 bridge is heavy and rounded, but posterior to the inguinal and anterior to the 



