205 



SCIENCE-GOSSIP. 



(i8S6), t. 6, f. I. The shell is somewhat solid, 

 disk-shaped, with a conical spire, hornish brown, 

 somewhat coarsely and regularly ribbed, and 

 decussated with spiral lines above and below, but 

 somewhat smoother below, and is widely, deeply 

 umbilicated. It is composed of six and a-half 

 regularly coiled whorls, which widen very slowly ; 

 the last whorl descends a little anteriorly, and 

 is angulated at the periphery, which is pro- 

 vided with a coarse laciniated fringe. The 

 peristome is white, a little thickened and 

 reflexed, and the aperture is rounded, without 

 armature, while the parietal callus has a raised 

 flexuous ridge which is almost united to the 

 margins of the peristome. The parietal armature 

 consists of a strong vertical lunate plate, the 

 convex side facing the aperture and only slightly 

 deflexed posteriorly at the lower extremity. On 

 the anterior side are found two short horizontal 

 folds in a line with the two extremities of the 

 vertical plate ; midway between these folds is a 

 denticle (see fig. 30a, which shows the shell with 

 a part of the outer wall removed, exposing both 

 armatures from the anterior side, and fig. 30^, 

 which gives the posterior view, while fig. 30^ 

 shows the inner wall separately ; all the figures 

 are enlarged). The palatal armature consists 

 of a small, short horizontal fold near the 

 suture, and four stouter and larger, nearly hori- 

 zontal folds, descending a little posteriorly (the 

 second and fifth being a little longer than the third 

 and fourth), and lastly, a short horizontal fold near 

 the lower suture (see figs. 30a and b). The speci- 

 men figured is in Mr. Ponsonby's collection, and 

 measures 14-5 millimetres in diameter. Mr. 

 Gredler has kindly placed at my disposal five 

 specimens, only one of which, however, has the 

 median parietal denticle ; two of the specimens 

 measure only 11 5 millimetres in diameter, two 

 others 14 millimetres, and one 13-5 millimetres; 



a be 



Fig. 30. — Plectopylis laminifera. 



they also vary a little in the height of the spire, 

 some being more flattened than others. The species 

 is closely allied to Plectopylis fimbriosa (see ante 

 p. 179, fig. 24) ; its nearest ally, however, is 

 P. reservata, which we shall have to consider in a 

 future paper. 



Several other species of the Chinese group re- 

 main to be dealt with, but exigencies of illustra- 

 tion again compel me to break into the continuity 

 of the series, and to revert to the Burmese and 

 Indian 'jpecies. 



Plectopylis serica (figs. 3ia-f) was described and 

 figured in the " Proceedings of the Zoological 

 Society," 1874, p. 608, t. 73, f. 5, by Lieut. - 

 Colonel Godwin-Austen, who first collected speci- 

 mens on the peak of Henozdan, Burrail range, 

 Naga Hills. Later he again found it abundant 

 above 5,000 feet on the same range, as far east 

 as the Kopameda ridge. He further states that 

 it is essentially a forest species, found in the 

 dead leaves and moss. The species was also 



a be 



Fig. 31. — Plectopylis serica. 



figured in Hanley and Theobald's " Conchologia 

 Indica," t. 132, ff. 8 and g (1875), but by an 

 error the name was printed sericata. The shell 

 is dextral, disk-shaped, with a slightly raised spire, 

 and is composed of seven narrow, closely-coiled 

 whorls. It is of a dark corneous brown above, 

 paler below, with narrow, oblique brown bands, 

 especially conspicuous below, running parallel with 

 the lines of growth. A distinctly angular, raised 

 ridge runs a little above the suture nearly to the 

 apex, the last whorl being bi-angulated at the 

 periphery. It is regularly and finely ribbed, and 

 distinctly decussated by microscopic spiral lines. 

 The last whorl descends but little anteriorly, the 

 peristome is a little thickened and reflexed, the 

 upper part of its outer margin being slightly 

 inflexed ; the parietal callus bears a very slightly 

 raised curved ridge, which is united to the margins 

 of the peristome, there being only a slight notch at 

 the lower junction. The parietal armature consists 

 of a single vertical plate, which descends a little 

 obliquely towards the aperture ; the upper ex- 

 tremity gives off on both sides a very short support, 

 and at the lower extremity, also on both sides, a 

 stronger support, the anterior one being a little 

 lower than the posterior one (see fig. 31a). The 

 palatal armature consists of five more or less 

 oblique horizontal folds ; the first is longest, 

 flexuous, and descends a little posteriorly ; the 

 second is horizontal, and bifurcates posteriorly, 

 the upper arm straight, the lower descending 

 obliquely ; the third, shorter, at first proceeding 

 horizontally, about the middle deflecting obliquely at 

 an angle of about 100 degrees ; the fourth is a little 

 longer, ascends a little at first and then deflects 

 posteriorly at an angle of 90 degrees ; the fifth 

 is shortest, horizontal, near the lower suture and 

 parallel to it (see fig. 316, which shows the 

 armatures, parietal and palatal, from the posterior 

 side, and fig. 3 if, which shows the inside of the 

 outer wall, with its palatal folds; all the figures 



