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 ^^ide 

 and deep. Parietal wall with a short entei'ing flexuous fold 

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

 and at one-third of the circumference from the aperture, \a ith 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 ; 

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

 vertical ridge, which deflects below Ihe fifth fold posteriorly and 

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



*' Major diam. K3 nun., min. 11 nun., alt. G mm." (Gitde 



Hah. Assam : Naga Hills. 



P. miispratti somewhat resembles P. n((f/aetisis, but the armature 

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

 parietal and palatal armatures, while fig. 37 f 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, Gucle, Science Gossip, n, s. vi, 1899, p. 15, fig. 97. 

 Plectopylis (Chersaecia) tnisteni, Gude, tom. 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 64, flattened above, rounded below, 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. 



