624 PROCEEDINGS OF THE ACADEMY OF [Dec. , 



d?. Lunella slightly curving inward below, not united 

 above with the upper palatal plica (fig. 8). 

 Clausilium rapidly tapering to the mucronate 



apex, Group of C. munus. 



d l . Lunella straight, joined to the middle of the 



upper and lower palatal plicae, like the letter 



I (fig. 1), . . . Group of C. aulacophora. 



c 2 . Superior and spiral lamellae contiguous or separated; 



lunella curving inward below, joining the short 



palatal plica above. Clausilium unusually straight 



and flat, rounded at the apex, Group of C. Pinto. 



A somewhat different sequence of groups would result from using 

 the characters of the clausilium for the primary divisions, but 

 while probably more natural, such an arrangement would be more 

 difficult in practical use. The clausilium is variously specialized 

 in the groups of C. ptychochila, G. munus and C. Pinto, much 

 alike in the other groups. The only species, so far as I know, not 

 provided for in the above key is C. platydera, which belongs with- 

 out doubt to the platyauehen group, but has the receding and 

 straightened inferior lamella of the other division; but there are 

 also some forms partially intermediate between the groups of (7. 

 validiuscula, C. sublunellata and C. aulaeophora, and further 

 knowledge will doubtless reveal various other intermediate species. 

 The group of C. validiuscula is probably a composite one. 



Group of C. sublunellata. 

 'Clausilia sericina var. rhopalia nov. 



Shell rimate, fusiform, rather obese below, the upper half atten- 

 uated; pale yellow; very finely striate throughout, the sculpture not 

 coarser on the last whorl. Outlines concave above, the apex 

 obtuse. Whorls 10, moderately convex, the last compressed later- 

 ally. Aperture ovate, somewhat oblique; peristome continuous, 

 white, reflexed and thickened, the upper margin in contact with 

 preceding whorl. Superior lamella oblique, marginal, continuous 

 with the spiral lamella which ascends to the middle of the ventral 

 side. Inferior lamella thick and forming a rather conspicuous 

 fold deep in the aperture, straightly ascending within, and pene- 

 trating as far as the spiral lamella. SubcolumelJar lamella deeply 

 immersed, terminating about a half whorl within. Principal plica 

 visible deep in the throat, ascending to a lateral position. Upper 



