512 PROCEEDINGS OF THE ACADEMY OF [DeC, 



pi-iiicipal plica, but curving down at the inner end. Clausiliuin Zap- 

 tychoid, with an angular projection near the middle of the palatal 

 margin. Type C. hivincta. {Thaumaloptyx , w^onderful fold.) 



This group is proposed for a marvellously specialized ClamUia. The 

 shell is not in the least rimate, the columellar and parietal margins of 

 the peristome being wholly adnate to the whorl, represented by a thin- 

 edged callus spread upon the whorl. It has some resemblance to 

 Selenoptyx in the deeply receding closing apparatus, the abruptly bent 

 inferior lamella Avithin the last whorl, the shape of the combined 

 upper palatal plica and lunella, and in the form of the clausilium. 



Clausilia bivincta n. sp. PI. XXXIV, figs. 45, 46. 



Shell slenderly fusiform, slowly tapering above to the rather large, 

 obtuse apex; thin, yellowish-corneous, subtransparent. Surface 

 glossy, faintly striatulate, the last whorl slightly striate behind the 

 lip. Whorls 8 to 9, the upper ones quite convex, the penultimate whorl 

 largest, the last whorl tapering, constricted around the middle as though 

 bound in by two tightly encircling cords. Aperture irregularly piri- 

 form, the outer and basal lips expanded, narrowly reflexed, not thick- 

 ened within; outer lip sinuous, being arched forward above the middle, 

 retracted at sinulus and base. The columellar and parietal lips are, 

 reflexed, and ivholly adnate, appearing only as a whitish callus spreading 

 upon the last whorl. The superior lamella is very small, thin and 

 oblique, not attaining the margin, continuous with the spiral lamella, 

 which is low within the back, but becomes high on the ventral side. 

 It penetrates past the aperture to the middle of the left side. The 

 inferior lamella recedes so as to be invisible from in front; within the 

 back it ascends vertically a short distance, then turns abruptly and 

 horizontally to the left, and then again ascends in a very wide plate 

 to its insertion. It does not penetrate parallel to the spiral lamella. 

 The subcolumellar lamella emerges. The principal plica is one whorl 

 long, running from near the lip to the middle of the left side. The 

 upper palatal plica is as long as the principal plica and subparallel to it, 

 but it diverges somewhat forwardly, where it is visible in the mouth, 

 and its inner end (apparently representing the lunella) diverges still 

 more, running obliquely down to the suture, behind the posterior angle 

 of the aperture. The principal plica and the upper palatal plica are 

 visible through the shell, and appear like cords causing the constriction 

 of the last whorl. There are no other palatal plicae, but the sub- 

 columellar Tamella runs up on the palatal wall in the position of a 

 lower palatal plica. 



