igo Records of the Indian Museum. [Voiv. XIX, 



suture on all but the apical whorls and give it a fimbriated or 

 almost subspinose appearance. On the greater part of the shell 

 these ribs are obsolescent on the lower parts of the whorls, but 

 on the whole surface of the outer aspect of the body-whorl they 

 are well developed. The}' are absent from the first two and a 

 half whorls. The shell as a whole has a smooth and polished 

 surface. The aperture is subquadrate but varies somewhat in 

 outlines and proportions. It always has the angles rounded. The 

 armature consists of two obtuse, somewhat compressed teeth and 

 two elongate internal folds. We will describe first its external 

 appearance and then its internal structure. The actual orifice is 

 conspicuously trilobed owing to the unusually strong develop- 

 ment of the armature. The three lobes are unequal. The upper- 

 most is a narrow sinus lying between the outer lip and a strong 

 internal fold, which projects out of the orifice for a short distance 

 in the form of a ridge. The second lobe, which is considerably broad- 

 er, lies between this ridge and the columellar margin, while the 

 third, which is intermediate in size, is bounded externally by a blunt 

 tooth lying inside the outer lip at the base of the first lobe. There 

 is a second internal tooth near the inner anterior angle of the 

 orifice, while a second internal fold lies inside the columellar part 

 of the peristome. The peristome itself is thickened and a little 

 expanded. It is interrupted by the upper lobe or sinus of the 

 orifice, which is pointed and slightly curved, and is often imper- 

 fectly developed between the termination of the upper fold and 

 the upper extremity of the columella. 



The two folds and the two teeth may now be described in 

 detail. The upper fold arises on the floor of the shell about half 

 way up the body-whorl and runs down, following the twist of the 

 spiral, to emerge from the aperture at the upper extremity a short 

 distance within the outer margin. It has the form inside the shell 

 of a highly convex crest, but on the edge of the aperture assumes 

 that of a low ridge. It is rather thick as a whole and has a blunt, 

 but not thickened free edge. The lower fold, although less 

 conspicuous externally, is considerabl}^ longer and in other respects 

 better developed. It arises on the internal column near the suture 

 of the body-whorl and runs along the former as a convex crest, 

 diverging slightly from the line parallel to that of the upper fold. The 

 free margin is considerably thickened on the inner side. A broad 

 deep gutter, which expands somewhat towards the aperture, is 

 thus produced between the two folds. The foot slides along this 

 gutter as the animal emerges. The outer tooth represents on the 

 internal surface of the shell the external funnel-shaped depression 

 on the outer aspect and is thus to a considerable extent hollow. 

 It forms with the upper fold a narrow sinus in which the pulmonary 

 orifice and the anus lie when the animal is expanded. The inter- 

 nal or basal tooth is solid and is not represented by any external 

 depression. The depression on the inner aspect of the whorl is 

 represented internally by a barely perceptible thickening at the 

 outer extremity of the lower fold. 



