824 PROCEEDINGS OF THE ACADEMY OF [DeC, 



A key to the sections follows: 



I. — Limella 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 plicce. fulcrum or parallel lamella, 



Section Hcmizaptyx. 

 h^. — Shell thin; sutural -pMcce, fulcrum and parallel lamella 



developed, Section Zaptyx. 



a^. — Inferior lamella spirally ascending within the last whorl, 



usuall}^ projecting into the aperture; clausilium strongly 



curved. 



h. — Clausilium tapering distally to an acuminate apex; shell 



solid and strong, without sutural plicte or accessory 



lamellae within; no upper palatal plica. 



Section Stereozaptyx. 



h^. — 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 plicae present, . . Section Metazaptyx. 



cV — ClausUium buttressed on the outer face by an erect, 



transverse plate; shell without sutural plicse. 



Section Pamzaptyx. 

 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 plicae, 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. Thej' 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 lamellse, and often in the texture of the shells. 

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



