332 



SCIENCE-GOSSIP. 



ARMATURE OF HELICOID LAND SHELLS 



AND NEW FORMS OF PLECTOPYLIS. 



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



( CmtinueA from page 240. ) 



Plectopylis giardi (figs. 95a-c.), from Cao-Bang, 

 Tonkin, was described and figured by Dr. H. Fischer 

 in the " Bulletin Scientifique de la France et de la 

 Belgique," xxviii. (1898), p. 320, t. 17, ff. 17-21. 

 The shell is dextrous, very deeply and rather 

 widely umbilicated, brown, finely striated, and 

 decussated with microscopic spiral lines above. 

 The spire is depressed, conical, the apex prominent 

 and the sutvire distinctly impressed. There are 

 eight whorls, which increase slowly and regularly 

 and are somewhat flattened above and tumid 

 below ; the last rounded, obsoletely angulated 



b 



Fig. 95, Plectopylis giardi. 



above the periphery, descends shortly and sud- 

 denly in front. The aperture is oblique, sub- 

 circular; the peristome white, rounded, much 

 thickened and strongly reflexed, its margins being 

 united on the parietal callus by a strongly 

 thickened and raised flexvious ridge, which is 

 slightly notched at the junctions above and below. 

 Near the apertural ridge occurs a short but strong 

 oblique fold. (See figs. 95a and c.) The pai-ietal 

 armature consists of two strong obliquely diver- 

 gent vertical plates, the anterior one shorter, 

 with a slight support on each side at the lower 

 extremity ; a short, thin, horizontal fold occurs 

 immediately above it; the posterior one longer, 

 somewhat attenuated at the lower extremity but 



rather truncated above. (See fig. 95e, which 

 shows part of the parietal wall with its armature). 

 The palatal armatvire consists of six short folds : 

 the first thin, horizontal, near the suture ; the 

 next four stronger, semicircvilar, more or less 

 oblique, and intercalated between the two ver- 

 tical parietal plates ; the sixth long and thin. 

 The second of these folds is nearly straight, a 

 little attenu.ated at both extremities, while the 

 third, fourth, and fifth are almost vertical, 

 reflexed anteriorly above and posteriorly below. 

 Plectopylis giardi and the next species are allied 

 to P. schlumbergeri figured in this series of papers 

 (vol. iv., 1897, p. 138, f. 58), P. jovia (ihid., f. 59), 

 and P. villedaryi (ibid., p. 139, f. 60), but can be 

 distinguished at once by the double vertical 

 parietal plate. I am much indebted to Dr. H. 

 Fischer, who kindly allowed me to make use of 

 the photographs of the type shells, which are 

 copied in figs. 95a-d. Figs. 95e and / (enlarged) 

 are from a specimen, one of three collected by 

 Dr. Billet, obligingly furnished by Prof. Giard, 

 and now in my collection. This specimen measures : 

 major diameter, 20 millimetres ; minor diameter, 

 17-5 millimetres ; altitude, 12 millimetres. 



Plectopylis congesta( ' ), figs. 96a-/. A shell received 

 from Messrs. Sowerby and Fulton as P. giardi 

 proved upon examination to differ from that 

 species as well as from all other known forms of 



(^) Plectopylis covigiesfa, n. sp. (fig.96a-/). — Shell 

 dextrous, deeply and very widely umbilicated, 

 dark corneous brown, somewhat paler below, finely 

 striated and decussated with microscopic spiral 

 lines which become obsolete below the perij)hery. 

 Spire depressed, conical ; apex prominent ; suture 

 slightly impressed. Whorls eight, rounded, in- 

 creasing slowly and regularly, the last distantly 

 ribbed, suddenly descending somewhat deeply 

 in front; aperture oblique, subcircular. Peri- 

 stome pale fuscous, thickened and reflexed; the 

 margins united on the parietal callus by a strongly 

 raised flexuous ridge, slightly notched at the 

 junctions above and below. Parietal wall with a 

 strong horizontal entering median fold, running 

 parallel with the suture and united to the apertural 

 ridge. Parietal armature consisting of a strong 

 vertical plate, furnished above and below an- 

 teriorly with a slight ridge or support; viewed 

 laterally this plate is seen to be slightly notched 

 at the upper extremity; a second shorter and 

 thinner vertical plate, the lower half of which is 

 obliquely deflexed, occurs behind the first; the 

 lower extremities of the two plates are united by 

 a slight horizontal ridge. Palatal folds six ; the 

 first slight, horizontal ; the second, third, fourth, 

 and fifth semicircular, oblique > the sixth, hori- 

 zontal. — Major diameter, 16-18-5 millimetres; 

 minor diameter, 14-15 millimetres ; altitude, 9-10 

 mm. — Habitat, Tonidn. — Type in my collection. 



