30 HELICID^E. 



at its lower extremity a slightly ascending ridge and posteriorly 

 a short support ; it is deflected horizontally at its upper extremity, 

 and at about its middle it gives off an obliquely descending arm, 

 which deflects horizontally at its lower extremity. Palatal folds 

 five : the first, thin, horizontal, near the suture, a little indented 

 and reflexed opposite the upper extremity of the oblique parietal 

 fold ; the second, horizontal, a little shorter and deflected 

 posteriorly, provided with a small denticle a little above its 

 posterior extremity ; the third, still shorter, but broader, hori- 

 zontal, crescent-shaped, its concave side towards the fourth, which 

 is vertical, very strong, inclined towards the aperture ; near its 

 lower extremity on the posterior side occurs a minute denticle ; 

 the fifth is horizontal, short and very thin." (Gude.) 



Major diam. 18'5, minor 15'5 mm. ; alt. 6 mm. 



Hob. Probably Burma. 



P. cairnsi is flatter and more rounded in outline than P. bensoni ; 

 the whorls are more rounded and not angulated, the last whorl 

 widens less at the aperture, the suture is more impressed, 4^e 

 umbilicus less deep, and the peristome is white. The parietal 

 armature differs from that of P. bensoni and its allies in the 

 median fold being interrupted in the middle and separated from 

 the branched portion which is in the form of the Greek letter X, 

 and in the total absence of the horizontal fold near the lower 

 suture (see fig. 64 d, enlarged, which shows the parietal wall with 

 its folds). In the palatal armature there are also some minor 

 differences : the first horizontal fold is indented opposite the 

 upper arm of the branched parietal fold, a feature I have nob 

 observed in any other species ; the vertical plate is also much 

 narrower than in P. bensoni^ leaving more space for the soft 

 parts of the animal to emerge (see fig. 64 e, which shows both 

 armatures from the anterior side, and fig. 64 /, from the posterior 

 side, both enlarged) ; and, finally, the denticle behind the fifth 

 horizontal fold, present in every other known species of the 

 group of P. bensoni, is absent (see fig. 64 </, enlarged, which 

 shows the inside of the outer wall with the palatal armature 

 in situ). The figures are all based on the type which is in my 

 collection. 



112. Plectopylis cyclaspis, Benson. 



Helix catinus, Benson, A. M. N. H. ser. 3, iii, 1859, p. 185 (non 

 H. catinus, Pfeiffer, 1856). 



Helix cyclaspis, Benson, torn. cit. p. 273; Hanley & Theobald, 

 Conch. Ind. 1870, pi. 13, fig. 10. 



Helix (Plectopylis} cyclaspis, Benson, op. cit. v, 1860, p. 245 ; Godwin- 

 Austen, P. Z. S. 1874, pi. 74, fig. 10 (palatal armature) ; Nevill, 

 Hand List, i, 1878, p. 72. 



Helix (Atopa (Plectopylis)} cyclaspis, Try on, Man. Conch, ser. 2, iii, 

 1887, p. 164, pi. 35, fig. 9. 



