SCIENCE-GOSSIP. 



155 



plate, angulated above, and giving off at its lower 

 end tovkfards the aperture, a horizontal plate, 4 

 millimetres long, which slopes abruptly towards 

 the parietal wall and gradually loses itself, while 

 on the posterior side there is a very short ridge 

 abruptly sloping obliquely downwards (see figs. 

 iSa and b) ; about the middle of the vertical 

 plate a free horizontal plate occurs, about 7 

 millimetres long, separated from the vertical plate 

 by a distance of i millimetre, decreasing in 

 height as it approaches the aperture, and 

 then suddenly terminating (see fig. 18a.) The 

 palatal armature is very curious (see fig. i8c, 

 which shows it in situ), and consists of six folds : 

 the first straight and horizontal ; the second also 

 straight and horizontal, but with a small bifurca- 

 tion at the posterior end ; the third partly horizontal 

 and deflecting posteriorly at an obtuse angle ; 

 the fourth very short horizontally, descending ver- 

 tically for a short distance and then deflecting 

 posteriorly ; the fifth very short, fle.xuous, and nearly 

 vertical ; while, finally, the sixth is again almost 

 horizontal. A little below, and to the left of the 

 sixth fold, is a small tooth, while above, posteriorly 

 to the first fold, and almost in a line with the bifur- 

 cation of the second fold, are three minute teeth. 



Plectopylis perarcta (figs, iga-c) was described by 

 Mr. Blanford in the " Journal of the Asiatic Society 

 of Bengal," xxxiv. (1865), part 2, p. 75, and first 

 figured by Dr. L. Pfeiffer in " Novitates Con- 

 chologicae," iii. (1867-1869), t. 108, f. 13-15. The 



Fig. ig. — Plectopylis perarcta, 



armature was figured by Lieut. -Colonel Godwin- 

 Austen in the "Proceedings of the Zoological 

 Society" for 1874, t. 74, f. 4. The species was 

 discovered at Mya Leit Doung, near Ava, Upper 

 Burmah, but the specimen now figured is from 

 Hlindet, and is in the collection of Mr. Ponsonby. 

 The shell is sinistral, disk-shaped, somewhat thin and 

 fragile, and composed of six closely-coiled whorls, 

 ribbed regularly above, smoother below, widely and 

 deeply umbilicated. It measures 10 millimetres 

 in diameter. The parietal armature is composed 

 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. iga), 

 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. ly). 

 Another horizontal but very short lamella, below 

 the principal one, also rises close to the vertical 

 plate; a short free horizontal lamella is seen below 

 the vertical plate, but it does not pass beyond it 

 posteriorly (see fig. iga ; this third horizontal 

 lamella is also shown sideways in figs. 19^ and c). 

 Lieut. -Colonel Godwin-Austen, in comparing the 

 present species with Plectopylis pseitdophis, states 

 that the horizontal lamella is not continuous, and 

 it is shown to be interrupted in his figure (Proc. 

 Zool. Soc. 1874, p. 609, t. 74, f. 4), and again, in 

 describing Plectopylis bmchydiscus (Journ. Asiat. 

 Soc, Bengal, .\lviii. (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 figured by me with P. perarcta, 

 but as the second horizontal lamella is joined to 

 the vertical plate in P. pseudophis and in my 

 specimen this lamella is quite free, as stated to 

 be the case in P. perarcta, it is evident that my 

 shell is not P. pseudophis ; moreover, Mr. Blanford, 

 in describing the shell, states that from the centre 

 of the curved ridge at the aperture, "a lamella 

 runs up the whorl towards the parietal plication." 

 It may, therefore, safely be assumed that in 

 the type specimen the horizontal lamella is 

 not interrupted, and the question arises whether 

 the shell figured by Lieut. - Colonel Godwin- 

 Austen was perfect in having the horizontal 

 plate interrupted in the manner described. The 

 palatal armature is simple, and consists of four 

 short, somewhat strong horizontal folds, equi- 

 distant and parallel, with a smaller one above, 

 close to the suture, and two small ones in a line 

 with each other below, also near the suture (see 

 figs. 196 and c, the former figure showing the 

 posterior, and the latter the anterior ends of the 

 folds ; of the two bottom folds only one is visible 

 in either figure). 



Plectopylis sJiiroiensis (figs. 20iJ-i/) is allied to the 



Fig. 20.— Plectopylis slUroiaisis. 



preceding species, and is likewise sinistral, but the 

 shell is smaller, measuring 7-5 millimetres in 



