824 PROCEEDINGS OF THE ACADEMY OF [Dec., 



A key to the sections follows : 



I. Lunella oblique, straight, becoming more or less incurved below; 

 above united with or contiguous to a short or moderate upper 

 palatal plica, somewhat in the shape of the letter J (except in 

 a few forms where the upper palatal plica is absent), 

 a. Inferior lamella receding, obliquely ascending and straight- 

 ened within the last whorl; clausilium parallel-sided, 

 rounded or acuminate distally, usually rather straight 

 except near the filament. 



b. Shell without sutural plicae, fulcrum or parallel lamella, 



Section Hemizaptyx. 

 6 1 . Shell thin; sutural plicae, fulcrum and parallel lamella 



developed, Section Zaptyx. 



a 1 . Inferior lamella spirally ascending within the last whorl, 

 usually projecting into the aperture; clausilium strongly 

 curved. 



b. Clausilium tapering distally to an acuminate apex; shell 

 solid and strong, without sutural plicae or accessory 

 lamellae within; no upper palatal plica, 



Section Stereozaptyx. 



6 1 . Clausilium wide, the apex obtuse; shell thin, the inferior 

 lamella approaching the superior as a thin fold in 

 the aperture. 



c. Clausilium smooth on the outer (convex) face; 

 sutural plicse present, . . Section Metazaptyx. 

 c 1 . Clausilium buttressed on the outer face by an erect, 

 transverse plate; shell without sutural plicae, 



Section Parazaptyx. 



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

 plica, and curves inward at its upper end ; no superior lamella; 

 sutural plicse, fulcrum and parallel lamella developed. Clau- 

 silium short, deeply notched on the palatal side near the apex, 



Section Oligozaptyx. 



III. The upper palatal plica is very long, an extremely short lunella 

 branching from near its inner end ; superior lamella and sutural 

 plicse developed. Clausilium notched on the palatal side near 

 the apex, Section Diceratoptyx. 



These groups are new with the exception of Zaptyx. They are re- 

 viewed below except Stereozaptyx ( = group of C. entospira, Proc. Acad. 

 Nat. Sci. Phila., 1901, p. 644), type C. entospira Pils. No other species 

 of Stereozaptyx is known. 



Section HEMIZAPTYX nov. 



A group of small species differing from Zaptyx in lacking sutural 

 plicse and accessory lamellae, and often in the texture of the shells. 

 They are all small, mostly under 11 mm. long. Most of those known 



