SCIENCE-GOSSIP. 



133 



ARMATURE OF HELICOID LANDSHELLS 



AND NEW FORMS OF PLECTOPYLIS. 



By G. K. Gude. F.Z.S. 



(Continued jrom page 115.) 



'pLECTOPYLIS achatina var. infrafasciata (') 

 (figs. 84«-f) is still darker than the variety 

 ohesa, being of a blackish or purplish-brown. Like 

 that variety it is rounded in contour, but it is larger 

 and more flattened ; while the umbilicus is a little 

 more shallow and the peristome more flattened and 

 reflexed than in the type. The peristome is livid 

 purplish in colour, the left margin being paler and 

 the right margin a little inflected. A whitish or 

 bluish-white band below reaches from the umbilical 

 angulation to the lower suture. The armature is 

 similar to that of the type, but the horizontal 

 parietal fold near the lower suture is visible from 

 the aperture and terminates close to the ridge. 

 The specimen figured was received by me from 

 Mr. Robert Cairns. Four specimens in the 

 collection of Mr. E. L. Layard and one specimen 

 in the McAndrew collection (the latter labelled 

 " Plectopylis re/uga ") all belong to this form. The 

 shell figured in Hanley and Theobald's " Con- 

 chologia Indica," t. 57, f. 8 and g, and Martini 

 und Chemnitz " Conchylien Cabinet" (2) i. t. 66, 

 f. 28-30 (from Mergui, Burma), I also refer to 

 this variety. A specimen measuring 21 milli- 

 metres in diameter is in the collection of Mr. 

 Cairns, who also possesses four immature shells 



Fig. S^.— l'leclopylis achatina var. infiafasciata. 



in various stages of growth, all showing sets of 

 barriers similar to that of the immature Plectopylis 

 achatina shown in fig. 8ia. 



(') Plectopylis achatina var. infrafasciata, n. var. (figs. 84 

 a-c), differs from tlie type in being more rounded in contour, 

 and in the last whorl not widening at the aperture; tlie 

 umbilicus is more shallow and the peristome more flattened 

 and reflexed ; the right margin is a little depressed ; the shell 

 is blackish or purplish brown above, with a white or bluish 

 white band below, reaching from the umbilical angulation to 

 the lower suture; the peristome is purplish brown, the left 

 margin being paler. — Major diameter, 22 millimetres ; minor 

 diameter, 18 millimetres; altitude, 8 millimetres. — Habitat, 

 Limestone Rocks, Moulmain, Burma. — Type m my collection. 



October, 1898. — No. 53, Vol. V. 



5(7-f) I 



Plectopylis achatina var. venusta (2) (figs. 85. 

 is smaller than any form of P. achatina I have 

 seen. It is pale yellowish-white in colour, 

 flammulated with chestnut above and at the 

 sides. It resembles the variety obesa in the 

 deeper umbilicus, the sloping underside and ir 



Fig. 85.. 



b c 



-Plectopylis achatina var. venusta. 



the comparative height of the shell ; the median 

 parietal fold does not quite reach the apertural 

 ridge as in that variety, and the lower horizontal 

 parietal fold is not visible from the aperture ; it 

 resembles the type in the sudden widening of the 

 last whorl. The peristome is livid brown, the 

 right margin being a little depressed ; the left 

 margin is paler. The specimen figured was re- 

 ceived by me as Plectopylis pachystoma Theobald ; 

 but as I am not aware that this name was ever 

 published, and as I have seen other shells so 

 labelled, I consider it expedient to discard the 

 name altogether. A specimen in the collection of 

 Dr. von Mollendorff, likewise labelled P. pachy- 

 stoma, I am unable to separate from the present 

 variety, although it shows no flammulation and the 

 peristome is white ; in other respects it is identical. 

 Plectopylis achatina var. castanca (») (figs. SGa-c) 



(2) Plectopylis achatina var. venusta, n. var. (figs. Ss^-c) 

 differs from the type and the other varieties in being smaller! 

 It resembles the variety obesa in the deeper umbilicus, 

 in the sloping underside, in the comparative height of the' 

 shell, and in the median parietal fold not reaching the 

 apertural ridge, but the last wliorl widens more, as in the 

 type. In colour it is pale yellowish-white, flamnnilated with 

 chestnut above and at the side. The peristome is livid 

 brown, the left margin paler, the right margin a little 

 depressed.— Major diameter, 17 millimetres ; minor diameter, 

 14 millimetres; altitude, 7 millimetres. — Habitat, Burma. 

 — Type in my collection. 



(') Plectopylis achatina var. castanea, n. var. (figs. 86a-c), 

 differs from the type in being smaller in diameter and pro- 

 portionately higher ; it is darker in colour, being blackish- 

 brown above and a little paler below. It resembles the 

 variety obesa in being more romided in outline, in the last 

 whorl not widening suddenly at the aperture, in the sloping 

 underside, and in the median parietal fold not reaching quite 

 to the apertural ridge ; the last two and a-half whorls are more 

 strongly decussated above and below than in anv other form. 

 An obsolete keel is visible at the periphery.— Major diameter, 

 21 millimeters; minor diameter, ig millimetres- altitude, 8 

 millimetres.— Habitat, Hiirma.— Tvpe in my collection. 



F 



