G3y Pll()CEEDIX(;8 OF THE ACADEMY Ol" [DcC. , 



Inferior lamella obliquely or somewhat spirally ascetidiug withiu. 

 Siibcolumellar lamella emerging, usually in a group of lip-folds. 



Lunella ventral or lateral, rather straight above, united below to 

 a lower palatal plica. No upper palatal plica. 



The oblique end of the clausilium, disconnected superior and 

 spiral lamellte, and frequent development of a group of lip-fold'^ 

 are the chief characters of this group. It differs from the mikado 

 group ])y the absence of an upper palatal plica and the discontinu- 

 ous superior and spiral lamelko. The plication of the lip in the 

 region of the inferior and subcolumellar lamellce varies from 

 strongly developed to obsolete in each of the species known 

 among individuals from most localities. 



a. — Peristome notched on the left side of the superior lamella- 

 Shell obese below, the upper, attenuated portion thick, api- 

 cal whorl large; length about 15 mm., . C sururiensk- 

 a\ — Peristome not notched or emargiuate near the superior lamella- 

 b. — Early whorls almost always self-amputated in adults. 

 Length 17-25 mm., dependent upon the number of 

 whorls retained, as well as upon the size of the indi- 

 vidual; diam. 4^-6 mm., . . . . C. bilabrata. 

 b^. — Apex entire; shell slender, acutely tapering above, the 

 first whorl minute; length 12-15, diam. 3-3^ mm., 



C. Oscariana. 



Clausilia bilabrata Smith. PI. XXXM, figs. 17-24. 



ClausiU'a bilabrata E. A. Smith, Quarterly Jouru. of Conchology, I, 

 p. 120. Boettger, Jahrb. d. D. Malak. Ges., 1878, p. 103, wUh var. 

 ptycholmna, PI. 4, fig. 6. Kobelt, t. c, p. 96, PI. 9, fig. 12. Molleu- 

 dor£f,Nachr'bl. d. I). Malak. Ges., 1900, p. 109. 



As no good illustration of this species has appeared, it is figured 

 here for comparison with the two new forms of the same group, 

 and to show the local variations. 



The shell is strong, almost always truncate and plugged in 

 adults, 7 to 10 whorls usually remaining. It varies in color from 

 straw-yellow to rather dark brown. It is very finely striate, 

 attenuated above, the last whorl laterally compressed. Aperture 

 ovate, the peristome reHexed and well thickened, very shortly free 

 above, usually but not always corrugated by several or many folds 

 grouped around the subcolumellar lamella. The superior lamella 

 is marginal, rather small, and separated from or sometimes almost 

 continuous with the spiral lamella, which penetrates past the ven- 

 tral side. The inferior lamella recedes very deeply, is not visible 



