TORNATELLLNA. 167 



perplexa, the upper and lower denticles small, seen only in an 

 oblique view in the aperture, the median lamella strong and 

 high. The lower or sub-columellar denticle is sufficiently im- 

 mersed to be invisible in figure '11. The parietal lamella, at 

 this stage of growth, is somewhat triangular, especially as 

 viewed from the base ; and its free edge flares outward in the 

 middle. 



23. T. MICROSTOMA Quadras et Mlldff. PL 33, figs. 8, 12. 



Shell subrimate, oblong-conic, thin, subpellucid, delicately 

 striate, slightly shining, buff-corneous. Spire turrited, the 

 sides a little convex, apex acute. Whorls 6^, rather flat- 

 tened, parted by a slightly impressed suture, slowly increas- 

 ing, the last spirally impressed, subsulcate before the aper- 

 ture. Aperture rather oblique, rhombic. Peristome simple, 

 acute, the columellar margin a little dilated, spreading. Colu- 

 mella strongly twisted spirally, lamellarly entering, excised 

 above, projecting in a dentiform process externally. Parietal 

 lamella moderately elevated, produced far within ; a single 

 palatal plica remote from the margin. Length 3.5, diam. 1.7") 

 mm. 



In the young shell the columella is trilamellate, the parietal 

 lamella more elevated, last whorl having three internal trans- 

 verse denticulate ribs, which wholly disappear in adults 

 (Mlldff.). 



Marianne Is.: Guam (Quadras). 



Tornatellina (Lamellina) microstoma Q. et MLLDFF.. Xm-li- 

 riehtsblatt d. Deutechen Malak. Gtesellschaft, vol. 26. Feb., 

 1894, p. 16. 



This species is much more robust than T. subcyWndrica. It 

 resembles T. nitida Pse. in shape. The adult form is hardly 

 distinguishable from T. moellendorffiana. but when the two 

 are laid side by side, it is seen that microstoma has a just per- 

 ceptibly narrower spire, and the whorls are less convex. In 

 an oblique view in the mouth one can see a small ratlin- sharp 

 columellar fold close to the insertion and rather deep within 

 in microstoma, while moellendorffiana has a heavier, callous 

 fold. 



