836 PROCEEDINGS OF THE ACADEMY OF [Dec., 



lamella wholly immersed, subobsolete. Principal plica long, extending 

 from a ventral position nearly to the aperture. Lunella lateral, united 

 to the middle of a long, curved lower palatal plica, and with its upper 

 end continued inward in a shorter upper palatal plica, much as in C. 

 platydera and its allies. There are two minute sutural plicae and a 

 short lamella fulcrans. 



Length 7.8, diam. 1.7 mm. 



Clausilium (PL LVII, figs. 105, 106, 107, 108) rather short, parallel- 

 sided, abruptly bent at the apex and twisted into a sort of spout, 

 notched on the palatal side of the projecting apex. 



Tokunoshima, Osumi, at Matsubara. Types No. 87,589, A. N. S. P., 

 from No. 1,202 of Mr. Hirase's collection. 



This is one of the smallest as well as one of the most specialized of 

 Asiatic Clausilise. It is named in honor of my friend, Charles Hedley. 



The clausilium is both abruptly curved and twisted near the apex, 

 so that its true shape is not easily conveyed by figures. The apical 

 end, however, is well shown by figs. 105 and 108, while it is seen much 

 foreshortened in figs. 106 and 107. 



Section DICERATOPTYX nov. 



The glossy shell is Zaptychoid, the superior lamella developed, 

 inferior lamella receding, calloused below. Subcolumellar lamella 

 rising high on the palatal wall, dilated in a lateral position. Upper 

 palatal plica very long, an extremely short lunella descending from near 

 its inner end. Lamella fulcrans and parallela and sutural plica3 are 

 developed. Clausilium deeply excised as usual at the filament, and 

 with a deep notch excavated near the apex on the palatal side. 



The very long upper palatal plica and diminutive lunella, and the 

 peculiar clausilium, are characteristic. The dilated subcolumellar 

 lamella, which rises high on the palatal wall, takes the place of a lower 

 palatal plica. 



The clausilium resembles that of Oligozaptyx, but the notch near the 

 distal end has been independently evolved in the two groups ; that of 

 Diceratoptyx being adapted to fit over the dilated subcolumellar lamella, 

 while in Oligozaptyx the notch fits over the lower palatal plica, and 

 has been evolved with the evolution of the latter. 



The internal structure is partially shown in PL LVII, fig. 113: /, 

 fulcrum; p, parallel lamella; sp, spiral lamella; inf, inferior lamella; 

 sc, subcolumellar lamella. The characteristic dilation of the latter 

 is well shown, as well as its course upon the palatal wall of the shell, 

 through which it is seen by transparence. 



