116 



HELICID^. 



Original description : — " Shell dextral, discoid, widely umbili- 

 cated, rufous brown, coarsely and regularly ribbed, with scarcely 

 visible microscopic sculpture above, but strongly decussated with 

 spiral lines below, suture impressed. Whorls 6, convex, slowly 

 increasing, the last rapidly widening towards the aperture, not 

 angulated above, shortly descending in front. Aperture sub- 

 triangular ; peristome light brown, a little thickened and reflexed, 

 the margins converging ; parietal callus with a strongly raised 

 flexuous ridge, separated from both margins of the peristome. 

 Umbilicus very wide but shallow. Parietal wall, with an entering 

 flexuous horizontal fold, united to the ridge at the aperture, and 

 at one-third of the circumference from the aperture with one 

 crescent-shaped vertical plate, which has two small denticles, one 

 above and one below, on the anterior side. Palatal folds 6, the 

 first and sixth thin and horizontal, the other four short, broad, 

 and oblique." {Gude.) 



Major diam. 27, minor 21 mm. ; alt. 10 mm. 



Hob. Burma: Attaram. 



Fig. 56.— Plectopylis smiihiana. 



Two specimens in the Theobald collection in the British 

 Museum, labelled P. hrachyplecta, in spite of some external reseir.- 

 blance to that species, presented sufficient difl'ereuces tc induce 

 me to suspect that they were quite distinct, and upon opening- 

 one of them the difference in the armature quite confirmed this 

 suspicion. 



F. smithiana differs from P. Irachyplecta in being larger and 

 darker in colour. The ribs are coarser and the whorls more 

 convex ; the last whorl is not angulated above, and it \^idens 

 more towards the aperture. The pei-istome is less thickened and 

 more reflected, and the ridge of the parietal callus less stout but 

 more raised, while the umbilicus is wider and much more shallo\^'. 

 The horizontal parietal fold deflects more at the aperture, and 

 there is only one vertical plate (see fig. 56 d), which is crescent- 



