PLATE 31. 
. Upper surface of the third costal plate, right side, of the 7}onyæ circumsulcatus, 
nat. size. 
2. Articular margin of ditto; showing the natural curve and thickness of the plate. 
3. Peripheral margin of ditto; showing the groove. 
. Upper surface of the third costal plate, right side, of the ۸۵ marginatus. 
. Sutural margin of ditto. 
j. Peripheral margin of ditto. 
. Upper surface of a fragment of a costal plate of the Trionye pustulatus, nat. size. 
. Under surface of ditto, showing the large and prominent adherent rib. 
. Peripheral margin of ditto. 
