PLECTOPYLIS. 107 



marked decussating spiral lines above and below. Apex minutely 

 granulate, slightly raised above the flat spire, suture rather deeply 

 impressed. Whorls 6, convex above and at the periphery, the 

 last a little compressed behind the mouth, descending suddenly to 

 the aperture, which is oblique and roundly lunate; peristome 

 white, expanded all round ; margins joined by a somewhat curved 

 ridge, from the centre of which a lamella runs up the whorl 

 towards the parietal plication, which, however, it does not join. 

 The parietal vertical lamina is single, simple, rather short, slightly 

 curved, with a rudimentary transverse plait at the top. Two 

 free horizontal lamellae occur beneath that running to the aper- 

 ture, the lowest being the longest and thinnest, and running back 

 beneath the base of the vertical lamina. Palatal teeth 6, all 

 horizontal except the 4th and 5th, which are slightly oblique. 

 Umbilicus open, deep, exposing all the whorls. 



" Major diam. 11, minor 9 mm. ; alt. 4 mm." (Blanford.) 

 Hob. Upper Burma : Mya Leit Doung, near Ava (Blanford) ; 

 Hlindet (Spratt, Coll. Ponsonby). 



The specimen here figured is in Mr. Ponsonby's collection and 

 measures 10 millim. in diameter. The parietal armature is com- 

 posed of a broad vertical plate, angulated above, but gradually 

 decreasing towards the base, where it is also slightly deflected 

 posteriorly. A horizontal lamella rises anteriorly about its middle, 

 very close to it, yet distinctly separate (see fig. 50 a), proceeding 

 parallel to the whorl, deflecting with it towards the aperture and 

 joining the raised flexuous bilobed ridge of the parietal callus, 

 which is separate from the peristome (see fig. 50 c). Another 

 horizontal but very short lamella, below the principal one, also 

 rises close to the vertical plate ; a short free horizontal lamella is 



b 

 a c 



Fig. Z&.Plectopylis perarcta. 



seen below the vertical plate, but it does not pass beyond it 

 posteriorly (see fig. 50 a ; this third horizontal lamella is also 

 shown sideways in figs. 50 b and c). Lt.-Col. Godwin- Austen, 

 in comparing the present species with Plectopylis pseudophis 

 [now shown to be synonymous with P. leiophis^, states that 

 the horizontal lamella is not continuous, and it is shown to be 

 interrupted in his figure (Proc. Zool. Soc. 1874, p. 609, pi. 74, f. 4), 

 and again, in describing Plectopylis brachydiscus (Journ. Asiat. 

 Soc. Bengal, xlviii (1879), p. 2), he informs us that that species 

 resembles P. perarcta in this respect. The specimen here figured, 

 however, has the principal horizontal lamella continuous, a fact 

 which induced me at first to doubt the specific identity of the shell 



