170 



SCIENCE-GOSSIP. 



ARMATURE OF HELICOID LANDSHELLS. 



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



{Continued from page 139.) 



pLECTOPYLISpseiidophis (figs. 62a-c) fromThyet- 

 ^ myo, Pegu, was described and figured by Lieut. - 

 Colonel Godwin-Austen, in the "Proceedings of the 

 Zoological Society," 1S74, p. 610, t. 74, figs. 3 and 

 3(1. The shell is sinistral, disk-shaped, pale horny 

 in colour, and widely umbilicated The spire is a 

 little elevated, and the suture slightly impressed. 

 There are seven whorls, which increase slowly and 



Fig. ■Sz.—Pleclopylis fiseiuiuplns. (((.original; 6 and c, after 

 Godwin-Austen.) 



regularly ; the last whorl is subangulated above, 

 rounded below, and descends rather deeply and 

 suddenly in front. The aperture is rounded, and 

 the peristome is thickened and reflected, the 

 margins being connected by a raised flexuous ridge 

 on the parietal callus, slightly notched at the 

 junctions above and below. The parietal armature 

 consists of a strong vertical plate, deflected 

 posteriorly at the upper extremity, and giving off 

 at the lower extremity an obliquely descending 

 ridge posteriorly and a short horizontal fold 

 anteriorly ; the vertical plate is toothed in outline 

 in the upper half, the teeth intercalating with 

 three of the palatal folds (see fig. 62c). A long 

 horizontal fold rises close to the vertical plate 

 anteriorly, revolving as far as the aperture, where 

 it unites with the raised flexuous ridge ; a thin 

 -slight fold runs near to and parallel with the 



lower suture (see figs. 62b and c, which shows 

 the shell with part of the outer wall removed). 

 The palatal armature consists of six simple short 

 folds, the lowest three the longest and highest, the 

 sixth much arched outwards (see fig. 62c). To my 

 regret I have been unable to examine the armature 

 of this species, having seen but a single specimen, 

 which is in the British Museum ; this is shown in 

 fig. 62a ; it measures — major diameter, 12 milli- 

 metres ; minor diameter, 10 millimetres ; altitude, 

 5 millimetres. Figs. 62b and c are copied from 

 " Proceedings of the Zoological Society," 1874, t. 

 74, figs. 3 and sa. 



Plectopylis brahtiia (figs. 6^a-c), from Brahmakhund, 

 Eastern Assam, was described and figured by 

 Lieut. -Colonel Godwin-Austen in the "Journal of 

 the Asiatic Society of Bengal," xlviii. (1879), p. 3, 

 t. I, f. 3. The shell is sinistral, disk-shaped, pale 

 horny-brown, finely and regularly striated, with a 

 moderately wide umbilicus. The spire is slightly 

 raised, and the apex is a little elevated. There are 

 seven whorls, which are slightly convex, and increase 

 slowly and regularly ; the last is angular above, 

 rounded below, a little constricted behind the 

 peristome, and scarcely descending in front. The 

 aperture is obliquely lunate, and the peristome is 

 white, a little thickened and reflexed, the margins 

 being connected by a scarcely raised curved ridge 

 on- the parietal callus ; the ridge is notched 

 at the junctions above and below. The parietal 

 armature- consists of a strong vertical plate 

 having a short support posteriorly above and 

 below, and giving off anteriorly at the lower ex- 

 tremity a short horizontal fold ; above this are two 

 free longer horizontal folds, the upper one rising 

 close to the vertical plate, the lower one longer 



Fig. 63.— Plectopylis I'ahma. 



and rising a little further from the vertical fold. 

 A minute denticle occurs between the second and 

 third horizontal folds, and a horizontally elongated 

 denticle above the upper extremity of the vertical 

 fold ; a very thin slight fold runs near to and 

 parallel with the lower suture, uniting with the 

 ridge at the aperture (see fig. 6y, which .•:-hows the 



November, 1897. — No. 42, Vol. IV. 



