112 



mediana crassissima, ea atque infera multo tenuiore usque ad 

 peristoma extensis, tertia interposita a margine remote evanescente, 

 sed usque ad laminam internam verticalem, circiter tertiam partem 

 unius circuitus a margine aperturali distantem extensa; ultimo 

 anfractu intus supra laminam verticalem antice plicis sex crassius- 

 culis, postice plicis decem brevioribus atque tenuioribus instructo. 



" Diam. maj. 21'5, min. 17, et 6'5 diam. aut alt. apertune 7*5 mm. 



" Diam. spec, secundi minoris sunt : 18'5, 15, 5'8, 6*6 mm." 

 (Stoliczlca.) 



Hob. Burma : Shan States (Stoliczkd) Kuengan, Pegu 

 (Theobald). 



The two shells collected by Theobald, which were discovered by 

 Godwin-Austen and Nevill in the Indian Museum, Calcutta, and 

 described as a new species under the name of trilamellaris by 

 Godwin- Austen, were subsequently found by him to be identical 

 with Stoliczka's species (J. A. S. B. xlviii, 1879, p. 2). 



The parietal armature consists of a strong horizontal median 

 fold, revolving over nearly half of the outer whorl, and united to 

 the ridge at the aperture, but it is free posteriorly. A short 

 distance beyond it occurs a strong vertical lunate plate, which is 

 deflected posteriorly below, where it gives off a short support ; on 

 the anterior side of this vertical plate, also below, a strong hori- 

 zontal fold is given off, extending a little over half the length of 



Fig. 53. Plectopylis shanensis. 



the median fold. A third horizontal thin fold, close to the lower 

 suture, commences just below the vertical plate, and is united to 

 the ridge at the aperture (see fig. 53 d, which shows the shell 

 with the outer wall removed, and fig. 53 Z>, which gives the 

 posterior view of the parietal and palatal armature). All three 

 horizontal folds are visible from the aperture as seen in fig. 53 a. 

 The palatal armature is in two series : the anterior series consists 

 of six thin horizontal subequal folds, while the posterior series is 

 composed of nine short denticles arranged in a vertical row (see 

 fig. 53 c which shows the inside of the outer wall). The specimen 

 figured is in the British Museum, and measures major diam. 

 19'5 mm. ; minor diam. 15-5 mm.; alt. 6 mm.; it is from the 

 Shan States. A specimen in the McAndrew collection in the 

 University Museum of Zoology, Cambridge, labelled Plectopylis 

 repercussa, proved on examination to pertain to the species now 

 under consideration. It measures major diam. 20 mm. ; minor 

 diam. 15 mm. ; alt. 6 mm. 



