PLECTOPYLIS. 121 



106. Plectopylis lissochlamys, Gude. 



Plectopylis lissochlamys, Gude, Science Gossip, N. s. iv, 1897, p. 70, 

 fig. 53 (shell and armature) ; Journ. Malac. vii, 1898, p. 11, 

 fig. 8. 



Plectopylis (s. s.) lissochlamys, Gude, Science Gossip, N. s. vi, 1899, 

 p. 148. 



Original description : " Shell sinistral, solid, discoid, widely and 

 deeply urnbilicated, polished, corneous, finely and regularly ribbed, 

 decussated with minute spiral sculpture above. Suture impressed, 

 apex a little raised, spire depressed. Whorls 7, rounded, in- 

 creasing slowly, the last twice as wide as the penultimate, widening 

 towards the aperture, but not constricted behind the peristome. 

 Aperture rounded, elliptical ; peristome white, rather thin, re- 

 flexed ; margins a little converging. Parietal callus with a raised 

 flexuous ridge separated from both margins of the peristome by a 

 little notch. Umbilicus wide and deep. Parietal wall with a 

 short, entering, flexuous horizontal fold, which runs close up to 

 the ridge at the aperture, and at one-third of the circumference 

 from the mouth there are two rather thin transverse parallel 

 laminae descending obliquely backwards, the posterior one longest 

 and w r ith a short ridge posteriorly both at the upper and the 

 lower extremity ; the anterior one with a longer ridge anteriorly 

 at the upper extremity, and two short but stouter ridges at the 

 lower extremity, one anteriorly and one posteriorly ; below these 

 laminae occurs a thin horizontal fold close to the lower suture, 

 becoming attenuated but distinctly perceptible at the aperture, 

 where it unites with the flexuous ridge. Palatal folds 5, the three 

 upper horizontal, thin, the first and second with a denticle 

 posteriorly ; the fourth vertical, the upper part deflected anteriorly, 

 the lower part deflected posteriorly, with two denticles posteriorly, 

 one about the middle and one near the lower extremity ; the fifth 

 short, horizontal, indented at the middle, with a slight curved 

 denticle posteriorly. 



" Diam. major 19-20, minor 16-17 mm. ; alt. 6-7 mm." (Gude.) 



Hob. Burma. 



The present species was based upon two unnamed specimens 

 from Burma sent to me by the late Miss Linter. Among a 

 number of Plectopylis forwarded to me for inspection by the late 

 Dr. von Mollendorff were two shells labelled P. refuga which 

 proved to be identical with Miss Linters shells. P. lissochlamys 

 differs from P. magna in being much smaller and shining, as well 

 as paler in colour ; in shape and texture it resembles P. pulvinaris 

 which, however, is dextral and has a totally different armature. 

 It is allied to P. ponsonbyi but is more solid, darker coloured, and 

 more coarsely ribbed, while the last two whorls increase more 

 suddenly, and the last is not constricted behind the peristome as 

 is the case in that species. The two parietal laminae, moreover, 

 are much thinner (see fig. 59 e) and the anterior ridges of the 

 anterior lamina are much shorter and slighter ; they are parallel, 



