SCIENCE-GOSSIP. 



204 



ARMATURE OF HELICOID LANDSHELLS. 



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

 (Continued from page 181.) 



T N speaking of Plectopylis fimhriosa, var. azo7ta {ante 

 p. 180), I stated that the only difference 

 between its armature and that of the type, appeared 

 to be that the palatal folds were shorter and that 

 the tooth near the sixth fold was absent. Since 

 writing, the Rev. Vincenz Gredler, of Bozen, 

 Austria, who described the variety, has kindly 

 placed two additional specimens at my disposal, 

 and these confirm my statement. The specimens 

 are, however, a little smaller than my own, 

 measuring only 1 1 millimetres in diameter. 



Mr. Gredler has also favoured me with three 

 specimens of Plectopylis invia, two of which I opened 

 in order to ascertain whether the second vertical 

 parietal plate already referred to (ante p. 181) was 

 constant, and as both specimens possess this plate, 

 it may reasonably be inferred that it is a constant 

 feature. In this connection, however, it is worth 

 mentioning that Lieut. - Colonel Godwin - Austen 

 (Proceedings of the Zoological Society, 1874, 

 p. 609) records the presence of two vertical parietal 

 plates in a specimen of Plectopylis serica, a species 

 normally provided with only one vertical parietal 

 plate, and he thinks that to this reduplication of 

 structure is due the more compound forms of 

 armature in the Burmese species of the genus. 



The same naturalist draws my attention to the 

 fact that there must be an error in the second 

 locality (Dafia Hills), mentioned by me for Plectopylis 

 shivoiensis {ante p. 156), as he believes that no 

 European has been in those hills since he collected 

 there, and he did not find the species in question. 

 The shell I figured as from the Dafla Hills is, in 

 Mr. Ponsonby's collection, so labelled, but, as it 

 was collected by Mr. Godwin-Austen, the locality 

 may now, on his authority, be safely altered to 

 Shiroifurar, which is 150 miles from the Dafla 

 Hills, and is the place from which the species 

 was originally described. 



Plectopylis stenochila (figs. 29 a~d), from Badung, 

 in the Chinese province of Hoo-Pe, was described 

 by Dr. von Mollendorff in the " Nachrichtsblatt 

 der Deutschen Malakazoologischen Gesellschaft," 

 1885, p. 165, and in the " Jahrbuch " of the same 

 society, xiii. (1886), p. i85. The shell is disk- 

 shaped, with a slightly elevated spire, and is com- 

 posed of six and a-half or seven whorls, which are 

 closely coiled and increase very slowly and regu- 

 larly, the last whorl descending a little anteriorly. 

 It is very finely and regularly ribbed and decussated 

 by fine spiral Hnes both above and below ; in addi- 

 tion the periostracum is raised into deciduous plaits, 

 which are especially conspicuous below, and form 



January, 1897.— No. 32, Vol. 3. 



a laciniated fringe round the angular periphery. 

 The peristome is white, a little thickened and 

 reflexed, while the parietal callus forms a slightly 

 raised, scarcely flexuous ridge which is separate from 

 both margins of the peristome ; the aperture is 

 almost round and is without folds. The parietal 

 armature consists of a somewhat strong vertical 

 lunate plate, its convex side facing the aperture and 



Fig. 29. — Plectopylis stenochila. 



a little deflexed posteriorly at the lower extremity. 

 On the anterior side there are, besides two short 

 horizontal folds, one above and one below, in a 

 line with the two extremities of the vertical plate, 

 and between these two folds occur four small 

 denticles, the two lower of which are united so 

 as to form a double one (see fig. 2gb). The 

 palatal armature consists of six folds : the first, 

 short horizontal and near the suture ; the second, 

 third, fourth, and fifth larger and stronger, parallel 

 to each other and descending a little obliquely 

 posteriorly; and the sixth again short, horizontal, 

 and near the lower suture (see fig. 2gd, which 

 shows both armatures from the posterior side, and 

 fig. 29c, which shows the inside of the outer wall 

 with its palatal folds). The specimen figured is in 

 Mr. Ponsonby's collection, and measures 8 milli- 

 metres in diameter. Mr. Gredler has favoured me 

 with three additional specimens, which differ slightly 

 from the one figured in having only one simple 

 besides the double denticle on the parietal wall. 

 The species is closely allied in its armature to 

 Plectopylis multispira {ante p. 181, fig. 27), but the 

 shell is smaller, more raised in the spire, and has 

 one whorl less, while it is less shining and trans- 

 lucent than that species. On the other hand it is 

 also allied to Plectopylis murata, to be considered in 

 a future article. 



Plectopylis laminifera (figs, -^oa-c), from Hoo-Pe, 

 China, was described by Dr. von Mollendorff, in 

 the "Nachrichtsblatt der Deutschen Malakazoo- 

 logischen Gesellschaft," 1885, page 164, and figured 

 in the "Jahrbuch" of the same society, xiii. 



