36 



SCIENCE-GOSSIP. 



ARMATURE OF HELICOID LANDSHELLS, 



With a New Form of Plectopylis. 



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



{Continiieil from page ii.) 



pLECTOPYLIS shanensis (figs. j^Sa-d), from 

 ■'• Burma, was described b y Dr. F. Stoliczka in the 

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

 (1873), p. 170, and figured in Hanley and 

 Theobald's " Conchologia Indica " t. 149, ff, 8 and 9 

 (1876). Lieut. -Colonel Godwin-Austen described a 

 supposed new species, under the name of Plectopylis 

 tyihimellaris, in the " Proceedings of the Zoological 



Fig. i^S. — Plectopylis shanensis. 



Society," 1875, p. 43, but he subsequently found it to 

 be identical with the present species. ("Journal of 

 the Asiatic Society of Bengal," xlviii. (1879), p. 2.,) 

 Mr. Nevill in his Handlist, p. 71, records speci- 

 mens from Kuengan, Pegu. As the armature 

 of this shell has never been figured, I am pleased to 

 have an opportunity of now illustrating it. The 

 shell is sinistral, discoid, with the apex a little 

 raised ; it is irregularly ribbed above and provided 

 with fine spiral sculpture. There are from 6J to 7 

 whorls, which are a little convex above, and rounded 

 below ; the last being much widened towards 

 the aperture and abruptly and deeply deflexed. 

 The umbilicus is wide and deep, and the aperture 

 widely lunate. The peristome is white, strongly 

 reflected and thickened, and the margins are united 

 by a strong raised flexuous ridge, notched above 

 and below. The parietal armature consists of a 

 strong horizontal median fold, revolving over nearly 

 half of the outer whorl, and united to the ridge at 

 the aperture, but it is free posteriorly. A short 

 distance beyond it occurs a strong vertical lunate 

 plate, which is deflected posteriorly below, where 

 it gives off a short support ; on the anterior side of 

 this vertical plate, also below, a strong horizontal 

 fold is given off, extending a little over half the 

 length of the median fold. A third horizontal thin 

 fold, close to the lower suture, commences just 

 below the vertical plate, and is united to the ridge 

 at the aperture (see fig. ^8d, which shows the 

 shell with the outer wall removed, and fig. 486, 

 which gives the posterior view of the parietal and 

 palatal armature). All three horizontal folds are 

 visible from the aperture as seen in fig. 48^. 

 The palatal armature is in two series : the 



anterior series consists of six thin horizontal sub- 

 equal folds, while the posterior series is composed 

 of nine short denticles arranged in a vertical row 

 (see fig. 4Sf, which shows the inside of the outer 

 wall). The specimen figured is in the British 

 Museum, and measures — major diam., 19J milli- 

 metres ; minor diam., 15J millimetres ; axis, 6 milli- 

 metres ; it is from the Shan States. A specimen 

 in the McAndrew collection in the University 

 Museum of Zoology, Cambridge, labelled Plectopylis 

 repercussa, proved on examination to pertain to the 

 species now under consideration. It measures — 

 major diam., 20 millimetres ; minor diam., 15 

 millimetres ; axis, 6 millimetres. 



Plectopylis stenochila va.r. basilia Q) (figs. 49a-c), from 

 Badung, Province of Hoo-Pe, was sent to me by 

 Professor Oscar Boettger, of Frankfort. It has a 

 more conical spire and the whorls are more flattened 

 than in the type (see ante vol. iii., p. 204, f. 29) ; 

 the periphery is acutely keeled, while in the type 

 it is rounded. The parietal armature differs in 

 having only four simple denticles anteriorly to the 

 vertical plate, the second denticle being very 



Fig. ^^.— Plectopylis stenochila, var. basilia. 



minute (see fig. 49;) ; the palatal armature is 

 identical with that of the type. 



Plectopylis emoriens (figs, ^oa-d), from the 

 Province of Hou-Nan, China, was described by 

 Mr. Vincenz Gredler in the " Jahrbuch der 

 Deutschen Malakozoologischen Gesellschaft," viii. 

 (1881), p. 15. Mr. Heude, in Part i of his " Notes 

 sur les Mollusques Terrestres de la Vallee du 

 Fleuve Bleu," published in the " Memoires con- 

 cernant I'Histoire Naturelle de I'Empire Chinois " 

 (1882), p. 34, considered this form to be a variety 

 of Plectopylis fimbriosa. The two forms, however, 



(') Plectopylis stenochila, var. basilia, n. var., diflers from 

 the type in the more conical spire, the more flattened whorls 

 and the acutely keeled periphery.— Diani,, 6-y mUl^etres. 

 Habitat, Badung, Province Hoo-P^, China. 



July, 1897.— No. 38, Vol. IV. 



