138 



SCIENCE-GOSSIP. 



ARMATURE OF HELICOID LANDSHELLS. 



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

 (Continued from page 103.) 



pLECTOPYLIS SCHLUMBERGERI (figs. 58 

 a and b), from Halong Bay and Elephant Moun- 

 tain, Tonkin, was described and figured by Mr. J. 

 Morlet, in the "Journal de Conchyliologie," xxxiv. 

 (1886), pp. 259 and 272, t. 12, f. 2. The shell is 

 dextral, discoid, solid, and widely umbilicated ; it 

 is shining, brown, coarsely striated and decussated 

 by spiral lines above, smooth below. The spire is 

 a little raised and there are seven whorls, which 

 are obsoletely keeled above, and subangulated 



Fig. ^8.—P!ectopylis schlumbergeri. {a, original; 

 b, after IMorlet.) 



below ; the last whorl does not descend in front ; 

 umbilicus deep, funnel-shaped. The aperture is 

 ear-shaped, and the peristome is white, thickened 

 and reflexed, its margins united by a sinuous raised 

 ridge, which gives off about the middle, a short, 

 entering, obliquely ascending fold. The parietal 

 armature further consists of a vertical plate, 

 with a slight denticle anteriorly near its 

 lower extremity. The palatal armature consists of 

 six small, narrow teeth. I do not possess a speci- 

 men of this shell, and as there is only a single 

 specimen of this species in the British Museum, I 

 have not had an opportunity of examining the 

 armature ; consequently I have been obliged to 

 rely on the somewhat meagre description of Mr. 

 Morlet, and upon his figure of the armature (op. 

 cit. fig. 2c), which latter I have copied (fig. 58b 

 giving the anterior aspect of the parietal and 

 palatal armatures.) The shell is stated to measure — 

 major diameter, 26 millimetres ; minor diameter, 

 22 millimetres ; height, 12 millimetres ; but the 

 specimen in the British Museum (fig 58^) measures — 

 major diameter, ig millimetres ; minor diameter 

 16 millimetres; height, 85 millimetres. In ad- 

 dition to the original locality the species has been 

 collected at Nuy-Dong-Nay, Tonkin (Dautzenberg 

 and d'Hamonville, "Journal de Conchyliologie," 

 XXXV. (1887) p. 218). 



Plectopylis jovia (figs. 59 a and b), from Halong, 

 Tonkin, was described by Mr. Jules Mabille in the 

 ' ' Bulletin de la Societe Malacologique de France, " iv. 

 (1887), p. 99. It was figured by Mr. Pilsbry in his 

 " Manual of Conchology," ix. (1894), t. 40, figs. 1-4, 

 from specimens forming part of the original lot 



collected by the Abbe Vathelet. It is allied to 

 Plectopylis schlumbei'geri, and like that species it is, 

 unfortunately, represented by a single specimen in 

 the British Museum and I have in this case 

 also been unable to examine the armature. Mr. 

 Pilsbry's figure of the structures in question, 

 however, is so good, and his description so minute, 

 that I will copy both. 



" Shell depressed, discoidal, very broadly um- 

 bilicated, the umbilicus regular, funnel-shaped, 

 its width contained not quite two and a-half 

 times in the diameter of the shell ; solid, opaque, 

 obliquely striulate and decussated by sub-obsolete 

 microscopic spiral lines above ; reddish under a 

 (deciduous ?) yellowish-brown cuticle ; lustreless. 

 Spire slightly convex, composed of seven and a-half 

 very slowly increasing whorls ; the last whorl 

 wider, rather strongly deflexed in front, very convex 

 beneath, and obtusely subangulated around the 

 umbilicus. Aperture oblique, rotund-truncate, the 

 peristome well curved, strongly reflexed, its face 

 white and thickened, ends joined by an elevated lobe 

 of the parietal callus, from which an entering lamella 

 arises extending a short distance inward. At the 

 last third within the whorl it is obstructed by 

 a broad, curved, transverse parietal plate, the 

 convexity of the curve outward, the upper border 

 of it slightly scalloped ; a minute denticle stands 

 in front of the lower end of this plate. The outer 

 wall bears seven plicae : the two outer small, 

 parallel to the sutures ; the next to the lowest fold 



Fig. ^(j.— Plectopylis jovia. (a, original ; b, after Pilsbry.) 



very minute, situated somewhat back of the 

 others ; the four median larger and directed 

 obliquely across the whorl. Altitude, 13 milli- 

 metres; diameter, 29-31 millimetres. It is not 

 improbable that both jovia and villedaryi will prove 

 to be varietal forms of schlumbergeri " (Pilsbry, 

 "Manual of Conchology," viii. (1893), p. 156). 



Fig. 59&, enlarged, is copied from " Manual 

 of Conchology," ix. (1S94), t. 40, f. 4. The specimen 

 shown in fig. 59a is in the British Museum, and 



October, 1897.— No. 41, Vol. IV. 



