502 PROCEEDINGS OF THE ACADEMY OF [DeC, 



a\ — Inferior lamella ascending in a broad spiral curve within the 



last whorl, approaching the superior lamella. 



h. — Clausilium strongly tapering to the angular or narrowly 



rounded apex, not buttressed externally; fulcrum present ; 



sutural plica; weak or wanting, Section Stereozaptyx. 



b^. — Clausilium tapering to the blimtly angular apex, buttressed 



outside by an erect transverse plate; no sutural plica? 



or fulcrum; inferior lamella receding, 



Section Parazaptyx. 



U'. — Clausiliiun wide distally, the apex rounded; smooth outside. 



Shell thin, sutural plica? developed; inferior lamella 



approaching the superior in the aperture as a thin fold. 



Section Metazaptyx. 

 IT. — The lunella arises from the middle of a long, arched lower palatal 

 plica, and curves inward at its upper end; superior lamella 

 developed or wanting; inferior lamella spirally ascending 

 within ; sutural plica?, fulcrum and parallel lamella developed 

 Clausilium short, deeply notched on the palatal side near the 



apex, Section Oligozaptyx. 



III. — The upper palatal plica is ver}'^ long, an extremely short lunella 

 branching from near its inner end; inferior lamella spirally 

 ascending within; superior lamella and sutural plica? devel- 

 oi)ed. Clausilium notched on the palatal side near the apex, 



Section Diceratoptyx. 



I\'. — The lunella is merely a continuation oblicjuely downwards of the 



"inner end of the upper palatal plica, and its position is ventral 



in known species ; no sutural or lower palatal plica? or fulcrum ; 



inferior lamella receding, vertical below, then bent to the 



left within the back of the last whorl. Palatal margin of the 



clausilium more or less excised below the middle. 



a. — Peristome entire, the apertiire normally clausilioid; upj^er 



palatal plica and lunella together much shorter ikan the 



principal plica, Section Selenoptyx. 



a^. Peristome widely interrupted; shell imperforate, not in the 

 least rimate; the upper palatal plica with the lunella forms 

 a very long, slightly bowed fold, subparallel to the principal 

 plica, but diverging downward towards the inner end, 



Section Thaumatoptyx. 



Section HETEROZAPTYX Pils. 



Proc. A. N. S. Phila., 1905, p. 730, footnote. 



Shell like Hemizaptyx; the upper palatal plica either short (as in 

 Zaptyz) or very long, approaching the aperture, and sometimes it is 

 interrupted. The clausilium is deeply excised on the coluraellar 

 side at the filament, callous and sivollen outside near the palatal margin, 

 and either acuminate or rounded at the end. Type C. nnams {Hetero- 

 zaptyx, unlike Zaptyx). 



