SCIENCE-GOSSIP. 



231 



ARMATURE OF HELICOID LANDSHELLS 

 With New Species of Plectopylis. 

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



{Continued from page lyi.) 



pLECTOPYLIS secura (figs. 65a-d), from Si-lin, 

 in the Chinese province Kouang-Si, was 

 described by Mr. Heude in the "Journal de 

 Conchyliologie," xxxvii. (1889), p. 226, and figured 

 in the third part of his " Notes sur les Mollusques 

 terrestres de la Vallee du Fleuve bleu " (1890), 

 t. 38, f. 6. Not having been able to obtain a 

 specimen of this shell, I have been obliged to rely 

 upon Mr. Heude's description and to copy his 

 figures. The shell is described as dextral, discoid, 

 greenish horn-coloured, striated above, shining 

 below, and widely umbilicated, with the spire 

 flattened and the apex scarcely raised. There are 

 six rounded whorls, which increase regularly, the 

 last scarcely descending in front ; the aperture is 

 semi-lunate and strongly oblique ; the peristome 

 narrow and reflexed ; the margins are united by 

 a raised flexuous ridge on the parietal wall, and 

 there is an entering horizontal fold. The parietal 

 armature consists of a single vertical plate, which 

 appears to be a little deflected anteriorly below 

 (see fig. 6^d). The palatal armature, as figured, 

 appears to consist of six oblique folds, although 

 the author only mentions four in his diagnosis ; the 

 first fold is minute, situate near the upper suture, 

 the next four stout and oblique, and the sixth 

 thinner and apparently horizontal (see fig 6^d). 

 The measurements given are — major diameter, 



Fig. 65. — Plectopylis secura (after Heude). 



9 millimetres ; minor diameter, 7 millimetres ; 

 altitude, 4 millimetres. 



Plectopylis Icucochilus (i) (figs. 66a-e). Five shells, 

 labelled " Burma," without further indication of 



{'-) Plectopylis Icucochilus, n. sp. (figs. 66a-i')- — Shell 

 sinistral, rather solid, discoid, deeply and perspectively 

 umbilicated, pale yellovvisli-corneous finely and regularly 

 ribbed, ornamented with minute spiral sculpture. Suture 

 almost linear, spire depressed, ape.x scarcely raised. 

 Whorls seven to seven and a-half, a little rounded above, 

 rather tumid below, increasing slowly and regularly, 

 the last descending abruptly and rather deeply in 

 front. Aperture roundly oval; peristome white, a little 

 thickened and strongly reflexed, the margins a little converg- 

 ing; parietal callus with a slightly raised flexuous ridge, 

 separated from both margins of the peristome by a little 

 notch. Umbilicus deep, widely perspective. Parietal wall 



locality, received by the writer, from Mr. Hugh 

 Fulton, under the name of Plectopylis leiophis, proved 

 upon examination to be distinct, and to belong, in 

 fact, to a different group of Plectopylis. They 

 represent a species — for which I propose the name 



Fig. 66. — Plectopylis leucochilus. 



Plectopylis leucochilus — allied to P. ponsonbyi, but 

 differing from it in the more raised spire and in 

 having a deeper and more perspective umbilicus. 

 In the armature this new species differs from the 

 other members of the group of P. ponsonbyi in 

 having the upper parietal fold uninterrupted. 

 Figs. 66a-c show the shell in three different aspects, 

 natural size, while figs. 66d and e are enlarged ; the 

 former shows the parietal wall with its plates and 

 folds, and the latter the inside of the outer wall 

 with the folds and denticles. 



Plectopylis perrierae (-) (figs, dja-f). — Two .speci- 

 mens of an undescribed Plectopylis have been 



with two transverse oblique plates converging upwards, the 

 posterior one rather thin, slightly sinuous, and having a short 

 ridge posteriorly at the upper and lower extremities, the 

 anterior one shorter, but nmch stronger and stouter, having 

 an ascending ridge posteriorly above and a short stout support 

 posteriorly below ; on the anterior side are found two strong 

 horizontal folds, the lower stout and short and becoming 

 suddenly attenuated ; the upper fold long, rather thinner, 

 following the deflection of the last whorl and terminating 

 close to the ridge at the aperture, but not being united to it; 

 a very thin horizontal fold rises below the transverse plates 

 close to the lower suture, runs parallel with it, and terminates 

 at the ridge at the aperture. Palatal folds, five : the first near 

 the suture, straight and nearly horizontal ; the second a little 

 more oblique and deflected posteriorly ; the third nearly 

 horizontal, but more deflected posteriorly ; all three have a 

 slight indentation near the posterior extremity formiiig a 

 bead-like termination ; the fourth is vertical, deflected a little 

 anteriorly above and posteriorly below, having posteriorly a 

 small denticle near the lower extremity and another about 

 the nnddle ; the fifth is near the lower suture, horizontal and 

 deflected at both extremities.— Major diameter, 15-17 milli- 

 metres; minor diameter, 12-14 millimetres; altitude, 6-7 

 millimetres.— Habitat, Burma.— Type in my collection. 



(~) Plectopylis penieme, n. sp. (figs. 67<i-/).— Shell sinistral, 

 discoid, widely and deeply umbilicated, pale corneous, very 

 finely and regularly striated, and decussated by spiral lines. 

 Suture slightly impressed, spire flattened, apex a little raised, 

 whorls si.x to seven, increasing slowly and regularly, flattened 

 above, rounded below, the last angulated above the periphery 



January, iBgB. — No. 44, Vol. IV. 



