NO. 2292. 



NEW FOSSIL TURTLES— GILMORE. 



181 



eighth is reduced in size and suboval in form. Their principal dimen- 

 sions are given in the accompanying table. 



Measurements of neurals in millimeters. 



e Estimated. 



The first costals differ from those of all other members of the 

 genus in being narrower than the second pair of costals at their 

 proximal ends. From the second to the eighth the costals become 

 successively narrower on the proxunal end. The eighth pair meet 

 on the midline behind the eighth neural for only 8 millimeters. 



The ornamentation of the carapace resembles somewhat that of 

 Asjnderetes splcndidus, consisting of abrupt and sharp-topped 

 ridges which by their union inclose pits and furrows of irregular 

 size and form. They are largest on the middle of the lengths of the 

 costals, extending over nearly the whole surface of the reduced 

 posterior costals. There are usually 4 or 5 of these pits or furrows 

 in a 10-millimeter line. The pits dmiinish slightly in size along 

 the middle of the shell, but toward the free borders the pits grow 

 smaller, finally disappearing altogether, thus having a smooth band 

 around the border, extending somewhat inward from the beveled 

 surface, especially on the median costals. The scalloped borders of 

 the disk are beveled off from the top side to a sharp edge. Tlie ribs 

 projected beyond the ends of the costals, but their exact extension 

 can not be determined in the type, as all are missing. 



The presence of eight neurals, the comparatively narrow and deep 

 median excavation of the anterior end of the disk for the nuchal 

 and the apparently loose articulation of that bone with the first 

 costals, the presence of a full complement of neurals, is an assem^blage 

 of characters differing from all described species. 



It resembles the other known species of Aspideretes from the 

 Judith River, Belly River deposits, in having the shell broader 

 than long and in the general character of the ornamentation of the 

 shell. 



EXPLANATION OF PLATES. 



Plate 29. 



Carapace of Nevrankylus uyomingensis, No. 7581, U.S.N.M. Type. Superior view. 

 About one-third natural size. 



