SCIENCE-GOSSIP. 



37 



differ in many respects as indicated below, and I 

 therefore follow Mr. Gredler in regarding Plecio- 

 pylis emoriens as a valid species. It appears never 

 to have been illustrated, for the figure given 

 erroneously under this name by Mr. Tryon, 

 " Manual of Conchology," second series, iii. (1887), 



BM 



m 



Fig. 50. — Ptcctopyli's i-moiifiis. 



t. 34, ff. 32-35, copied from Mr. Heude's work, is 

 undoubtedly Plectopylis fimbriosa. The differences 

 between the two species are given in tabulated 

 form to facilitate comparison. 



Plectopylis fimbriosa : 

 apical whorl ribbed ; 

 strong spiral sculpture 

 on the upper surface ; 

 suture nut impressed ; 

 whorls 6, flattened ; peri- 

 phery acutely keeled ; 

 fringe of coarse laciniae, 

 persistent ; umbilicus very 

 deep, perspective ; diam., 

 13-15 millimetres. 



Plectopylis emoriens : 

 apical whorl smooth ; 

 spiral sculpture only 

 perceptible in young 

 specimens ; suture deeply 

 impressed ; whorls 41^, 

 rounded ; periphery ob- 

 tusely angled ; fringe of 

 fine liairs, deciduous ; 

 umbilicus moderately 

 deep; diam., 6-7 milli- 

 metres. 



The parietal armature is similar to that of 

 Plectopylis fimbriosa, but the palatal armature 

 slightly differs, in the folds being much shorter, 

 and the small tooth situated posteriorly to the 

 si.xth fold in P. fimbriosa is absent in P. cmoiiens, 

 and instead of it there is a minute denticle a 

 little above and posteriorly to the second fold 

 (see fig. 50^). The specimen figured is in my 

 collection and measures 7 millimetres in diameter. 

 The palatal folds are visible through the shell wall. 



Plectopylis rcserata (figs, ^la-e), from Tchen-K'eou, 

 China, was described and figured by Mr. Heude in 

 Part 2 of his " Notes sur les Mollusques terrestres 

 de la Vallee du Fleuve Bleu " (1885), p. 112, t. 30, 

 f. 3. The shell is disk-shaped, more or less 

 pellucid with flattened spire, pale corneous, 

 regularly and finely ribbed, decussated with very 

 fine spiral lines above and below, widely and 

 deeply umbilicated. It is composed of 6.^ regu- 

 larly coiled whorls, which widen slowly ; the 

 last whorl descends a little in front and is 

 acutely keeled at the periphery, which is provided 

 with a fringe of laciniae. The peristome is white, 

 a little thickened and refiexed. The aperture is 

 roundly lunate, the margins being united by a 

 raised flexuous ridge on the parietal callus, a 



little notched above and below at the junctions. 

 The parietal armature consists of a strong vertical 

 lunate plate, strongly deflected posteriorly down- 

 wards ; on its anterior side are found two slight, 

 short, horizontal folds in a line with the upper and 

 lower extremities of the vertical fold ; between 

 these are two, or sometimes three, small denticles, 

 elongated vertically, which in some specimens 

 have coalesced (see fig. ^id, which shows part of 

 the parietal wall). The palatal armature consists 

 of a small, thin, horizontal fold near the suture ; 

 next four stouter and longer horizontal folds united 

 by a slight vertical callus, and at equal distances 

 from each other ; and finally another thin, short, 

 horizontal fold near the lower suture (see fig. 51^, 

 which shows the inside of the outer wall). Plectopylis 

 reserata is closely allied to P. laminifera (see ante, 

 vol. iii., p. 205, fig. 30). It differs, however, in 

 being more pellucid and less solid, in the whorls 

 being flatter and in the umbilicus being much more 

 shallow. The parietal armature displays consider- 

 able differences ; the vertical plate is much more 

 oblique downwards, and the upper and lower 

 anterior folds are much thinner and shorter, while 



Fig. 51,— Plectopylis reserata. 



there are two or more denticles elongated vertically 

 between these two folds, whereas in P. laminifera 

 there is only one denticle, elongated horizontally, 

 and this is sometimes absent. The specimen 

 figured is from Patong, and is in the collection of 

 Mr. Gredler, Bozen, Austria ; it measures — major 

 diam., 13 millimetres; minor diam., 11 5millimetres; 

 axis, 5"5 millimetres. 



{To be continued.) 



