lO 



SCIENCE-GOSSIP. 



ARMATURE OF HELICOID LANDSHELLS, 



With a New Species of Plectopylis. 



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



(Continued from Vol. Hi., page 332.) 



pLECTOPYLIS muspratti (i) (figs. 45^-/). With a 

 number of Plectopylis kindly sent to me by 

 Colonel Beddome for inspection, were three shells 

 which he thought would prove to be new. Upon 

 examination I found them to differ from all the 

 described species, and now, therefore, publish 

 this form as a new species under the above 

 name, which was suggested by Colonel Beddome. 

 Plectopylis muspratti in outward appearance some- 

 what resembles Plectopylis nagaensis (vol. iii., p. 206, 

 fig- 33). but the armature is quite different. 

 The parietal armature (see figs. 45^ and d) consists 



Fig. 45.— Plectopylis muspratti. 



of a strong, vertical lunate plate, strongly deflected 

 posteriorly below, the convex side towards the 



(1) Plectopylis muspratti, n. sp. (figs. 45a-/).— Shell sinistral, 

 discoid, widely and deeply umbilicated, pale corneous, 

 streaked transversely with dull brown ; finely striated and 

 decussated with spiral lines, which are very distinct on the 

 upper surface, but less so below. Suture impressed, spire 

 a httle 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 leflexed, margins 

 converging. Parietal callus with a strongly raised flexuous 

 ridge, which is separated from both margins by a little notch. 

 Umbilicus wide and deep. Parietal wall with a short enter- 

 ing flexuous fold united to the ridge at the aperture, becoming 

 attenuated inwardly, and at one-third of the circumference 

 trom the aperture, with 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 farst free, with a small denticle posteriorly ; the second, 

 third, fourth, and fifth connected with each other by a vertical 

 ridge, which deflects below the fifth fold posteriorly and 

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

 —Major diameter, 13 millimetres; minor diameter, 11 milli- 

 metres ; axis 6 millimetres.-Habitat, Naga Hills, Assam. 

 —Type in Colonel Beddome's collection. 



Tune, 1897.— No. 37, Vol. IV. 



aperture ; below, on the anterior side, is a very 

 short horizontal fold ; a short, entering, flexuous, 

 horizontal fold occurs at the aperture and is joined 

 to the flexuous raised ridge which unites the twc 

 margins of the peristome. The palatal armature 

 consists of: first, a free, short, horizontal fold with 

 a small denticle posteriorly ; next, four short, 

 horizontal folds connected by a slight vertical 

 ridge about their middle ; the posterior halves of 

 the folds being thinner and slighter than the 

 anterior halves; the vertical ridge is continued 

 below the fifth fold, where it suddenly deflects 

 posteriorly and terminates in a small oblique 

 denticle ; below the fifth fold, a little nearer to the 

 aperture, is found a sixth fold, which, like the first, 

 is quite free (see fig. 45/, which shows the inner 

 side of part of the outer wall with its palatal folds, 

 and fig. 45^;, which gives the posterior view of 

 the parietal and palatal armatures). 



Plectopylis macromphalus (figs. 46a and b) was de- 

 scribed and figured by Mr, W. T. Blanford in the 

 "Journal of the Asiatic Society of Bengal," xxxix. 

 (1870), part 2, p. 17, t. 3, f. 14, and in Hanley and 

 Theobald's " Conchologia Indica," t. 83, ff. 8-10. 

 The armature was figured by Lieut. -Colonel 

 Godwin- Austen in the " Proceedings of the 

 Zoological Society." 1874, t- 73, f. i. The species 

 has been recorded from the Khasia, Dafla and 

 Naga Hills, in Assam. The shell is sinistral, 

 widely umbilicated, light corneous, with in- 

 cremental curved plicae, decussated by spiral 

 lirae above, somewhat smooth and shining below 

 It is composed of 4 J to 5I flattened narrow whorls, 

 the last being scarcely wider, subangulate above, 

 a little descending in front. The peristome is 

 whitish, a little thickened and reflexed, slightly 



a I, 



Fig. 46. — Plectopylis inacroiHphaliis. 



flattened on the upper, outer margin ; the margins 

 converge a little, and are joined by a thin callus on 

 the parietal wall. The parietal armature (see fig. 

 4Grt) consists of a strong vertical plate, which has a 

 minute, slightly elongated, horizontal denticle 

 posteriorly to its lower extremity. The palatal 

 armature is in two series (see fig. 466, which shows 

 the inside of the outer wall). Tho ?.nterior series 



