90 HELICID^E. 



impressed, spire a little conical. Whorls six and a half, scarcely 

 convex, slowly increasing, the last widening towards the aperture, 

 slightly angular above, descending suddenly in front, and a little 

 constricted behind the peristome. Aperture roundly lunate ; 

 peristome white, thickened and reflexed, margins converging. 

 Parietal callus with a strongly raised flexuous ridge, which is 

 separated from both margins by a little notch. Umbilicus wide 

 and deep. Parietal wall with a short entering flexuous fold 

 united to the ridge at the aperture, becoming attenuated inwardly, 

 and at one-third of the circumference from the aperture, with a 

 strong, crescent-shaped vertical plate, which is suddenly deflected 

 posteriorly at the lower extremity ; below this, on the anterior 

 side, occurs a very short, horizontal fold. Palatal folds six, 

 horizontal, short ; the first free, with a small denticle posteriorly ; 

 the second, third, fourth, and fifth connected with each other by a 

 vertical ridge, which deflects below the fifth fold posteriorly and 

 terminates in a small, oblique denticle ; the sixth again free. 



41 Major diam. 13 mm., min. 11 mm., alt. 6 mm." (Gude 



Hob. Assam : Naga Hills. 



P. muspratti somewhat resembles P. nagaensis, but the armature 

 is quite different. Fig. 37 d gives the posterior view of the 

 parietal and palatal armatures, while fig. 37 e exhibits the inner 

 wall with the parietal folds, and fig. 37/ the inside of the outer 

 wall with the palatal armature. 



87. Plectopylis austeni, Gude. 



Plectopylis austeni, Gude, Science Gossip, N, s. vi, 1899, p. 15, fig. 97. 

 Plectopylis ( Chersaecia) austeni, Gude, torn. cit. p. 148. 



Original description : " Shell sinistral, discoid, widely um- 

 bilicated, ochreous corneous, covered with a deciduous velvety 

 cuticle; finely and closely ribbed, decussated by raised spiral 

 lines, rather distant on the upper side. One of these spiral lines 

 forms a ridge or keel on the upper angle of the whorls above the 

 periphery, revolving above the suture as far as the third whorl. 

 Spire concave, apex a little raised, suture strongly impressed. 

 Whorls 6^, flattened above, rounded below r , obsoletely angulated 

 around the umbilicus : increasing slowly at first, the last widen- 

 ing rather suddenly, and descending half the width of the whorl 

 in front; aperture oblique, cordate. Peristome white, strongly 

 thickened and reflexed, the margins united by a strong raised 

 flexuous concave ridge, slightly notched at the junctions above 

 and below. Umbilicus wide and rather shallow. 



" Parietal armature consisting of a short median horizontal fold 

 close to the apertural ridge, and a second, longer and farther back, 

 rather elevated posteriorly, gradually descending on the shell-wall 

 anteriorly ; below its posterior extremity occurs a small denticle ; 

 still farther back is found a strong vertical crescent-shaped 

 plate, the upper and lower extremities of which are deflected 

 posteriorly. 



