NO. 2137. 



Tiro NEVr Fnsi^TL TrRTLEf^—CTLMOEE. 



645 



There nre se^en neiirtils, the seventh reaching the eighth pair of 

 costals, whereas in all other described species of tlie genns A.'^pl- 

 deretcs^ and Plastomenus as well, they never pass beyond the seventh 

 pair and often end with the sixth. 



The first nenral is octagonal, with the median anterior boi-der 

 notched for the prenenral, which is missing in this specimen. The 

 succeeding neurals are hexagonal, longer than wide, with the narrow 

 end forward as usual in the species of this genns. The dimensions 

 of the nenrals will be found in the accompanying table. 



Mcdsiircinciifs of nenrals. 



e=estimalod. 



There are nine pairs of costal bones, the ninth pair being very 

 small and are missing from the present specimen (plate 34, c. 9), but 

 the sutural borders show clearly the presence of this supernumerary 

 pair. The eighth and ninth pairs meet on the median line except on 

 the antero-median part of the former where the seventh neural is 

 slightly interposed betvveen them. The eighth pair meets on the 

 median line for a distance of 34 mm. The costal ribs project beyond 

 the edge of the carapace. The sixth of the right side projects 22 mm. 

 beyond the border and it lacks the tip. None of the others are so 

 perfectly preserved. The ribs are moderately broad, but occupy less 

 than half the width of the costal plate. Between the ribs the borders 

 of the costals have a thickness of from 6 to 7 mm.; through the rib 

 they are 10 mm. in thickness. 



On the outer ends of costals three, four, and five the sculpture 

 stops short of the edge leaving a narrow smooth border that re- 

 duces the thickness of the costal from 2 to 3 mm. less in thickness 

 than the sculptured portions. See figure 1, plate 35. 



The nuchal bone is represented by a small piece of the right end, 

 which remains in ])osition attached to the under side of the first costal, 

 as shown in plate 34, n. 



The plastron is represented by two small fragments, probably per- 

 taining to the hyoplastron. These show a surface ornamentation 

 quite distinct from that of the carapace. It is made up of a series of 

 short, raised, vermiculate ridges with intervening furrows of varying 



