179 



SCIENCE-GOSSIP. 



parietal armature consists of a single strong 

 vertical plate (see fig. 23a). Lieut. -Colonel 

 Godwin-Austen, in describing the armature (loc. 

 cit.), states that the parietal plate has only a slight 

 horizontal support above on the posterior side ; 

 in the tv/o specimens in my possession, however, 

 this plate has a similar support below ; these 

 supports consist of a tooth united to the vertical 

 plate by a slight callosity. Below this is a short 



Fig. 2^.—Plectopylis fitltoni. 



thin horizontal plate, a little indented in the 

 middle. The palatal armature (see fig. 236) 

 consists of : first, a short horizontal fold, close to 

 and parallel with the suture ; secondly, a longer 

 and stouter horizontal flexuous fold ; thirdly, 

 another horizontal fold, slightly indented in the 

 middle and deflexed posteriorly at an obtuse angle ; 

 fourthly and fifthly, two series each of two short 

 horizontal folds, the anterior ones slightly oblique, 

 with their lower ends towards the aperture, and the 

 posterior ones deflexed at an obtuse angle posteriorly; 

 and sixthly, near the base, a short slightly bent 

 fold, with the convex side turned towards the 

 lower suture. The specimen figured, which is 

 not quite mature, bears a second vertical plate on 

 the parietal wall (see fig. 23a), which appears to be 

 the remnant of the immature barriers formed before 

 the completion of the shell, for, as will be seen later 

 on, in this genus, as in Corilla (see ante p. go), the 

 armature is not confined to full-grown shells, but 

 occurs at various periods of their existence, the 

 earlier sets of plates and folds being absorbed after 

 the formation of the next set. A young specimen 

 in my collection, composed of five whorls, possesses 

 the armature a little beyond the place where four 

 and a-half whorls have been completed ; the 

 barriers are almost identical with the mature ones, 

 except that the folds are smaller and the second 

 and third palatal folds are deeply bilobed. A still 

 younger specimen of only four whorls has the 

 armature near the place where three and a-hal 

 whorls have been completed. Plectopylis fuUoni is 

 allied on the one hand to P. andersojii (see ante p. 

 154' fig- 17). the parietal armature being almost 

 identical, while the arrangement and structure of 

 the palatal folds connect it on the other hand with 

 P. pledostoma, to be considered in a subsequent 

 paper. 



The species of Plectopylis hitherto dealt with 

 belong to a group forming a section of the 



genus, the members of which, with perhaps one 

 exception, do not occur north of the Himalayan 

 range, but are confined to the vast tract to the 

 south of it, comprising India, Burma, and Farther 

 India. Before dealing with the remaining members 

 of this section, exigencies of illustration compel 

 me to consider the Chinese members of the genus, 

 which constitute another section characterized by 

 a glossy, more or less transparent shell and a 

 somewhat less complicated armature. All the 

 known species are dextral. 



Plectopylis Jjtnbi'iosa {&gs. 24a and b), was described 

 and figured by Dr. E. von Martens, in the " Jahrbuch 

 der Deutschen Malakazoologischen Gesellschaft," 

 ii. (1875), p. 128, t. 3, f. 6, from specimens col- 

 lected in the Province of Kiang-si of China : it 

 has subsequently been found in the Province of 

 Hou-Nan. Dr. O. F. von Mollendorff, in figuring 

 the armature of this species (op. cit. x. (1883), t. 12, 

 f. 11), has given only the anterior aspect of the 

 plates and folds, while my figure (fig. 24a) shows 

 the posterior view. The shell is disk-shaped, with 

 the spire a little elevated, subpellucid, corneous, 

 composed of six whorls slowly increasing ; strongly 

 and regularly ribbed above, with a strong spiral 

 sculpture, smoother and shining below, with a 

 yellowish band round the wide open umbilicus ; 

 angulated on the periphery, which is provided with 

 a fringe of coarse lacinia ; the white peristome is 

 strongly reflexed, and a little thickened, and the 

 parietal wall is without a callus ; the shell measures 

 15 millimetres in diameter. The parietal armature 

 consists of a strong, simple, vertical, lunate plate, 

 the convex side of which is turned towards the 

 aperture, and the lower extremity is somewhat 

 strongly deflexed posteriorly ; on the anterior side 

 are found two short horizontal teeth, one above 

 and one below, in a line with the extremities of the 

 vertical plate, the upper one being the stronger 

 of the two (see fig 246). The palatal armature 



Fig. 24. — Plectopylis fimbnosa. 



consists of six short, simple, horizontal folds, the 

 first near to and parallel with the suture, the 

 second longer and stouter, nearly opposite the 

 upper extremity of the parietal plate; the third, 

 fourth, fifth and sixth all parallel, equidistant, and 

 gradually decreasing in length downwards ; a small 

 tooth occurs a little above and posteriorly to the 

 sixth fold ; these folds are visible externally 

 through the shell wall. The three specimens in 

 my collection are from Kioo-Kiang, Province of 

 Kiang-Si, and are all identical in armature. One 



