SCIENCE-GOSSIP. 



103 



the preceding species, the armature has not been 

 illustrated, and I am glad to have an opportunity 

 of giving figures of it. The shell is dextral, finely 

 striated, and distantly ribbed above, finely striated 

 and shiuing below, light coriieous, pellucid, and 

 widely umbilicated The spire is a little elevated 

 and the suiur'u is distinctly impressed. There 

 are from six to six and a- half convex whorls, 

 which increase very slowly and regularly, the 

 last being carinated above the periphery, 

 rounded below, slowly and shortly descending 

 in front. The aperture is roundly lunate, 

 oblique ; the peristome white, a little thickened 

 and reflexed, its margins being connected by a 

 much raised curved plate on the parietal wall. 



S] 



Fig. ^G.—Plectopylis schistopiyclna. 



slightly notched at the junctions above and below. 

 The parietal armature consists of a strong vertical 

 plate, having a short support posteriorly at the 

 lower extremity, and two similar supports ante- 

 riorly, one above and one below (see fig. 56^, which 

 shows the parietal wall with its fold). The palatal 

 armature consists of eight small denticles (above 

 which are a fold and a minute denticle) in two 

 series of four each, the lowest denticle of both 

 series being smaller than the others and nearer 

 together ; they are all more or less elongated, 

 those of the posterior series being oblique, except 

 the lowest, which is horizontal, while those of the 

 anterior series are all horizontal ; above these 

 denticles occurs the fold just mentioned, which 

 is thin, horizontal, interrupted slightly near its 

 posterior extremity, and becoming attenuated 

 anteriorly, while near its posterior extremity is 

 found the minute denticle (see fig. 56^, which 

 shows the inside of the outer wall with its fold and 

 denticles) ; these structures are visible through 

 the shell-wall. The specimen figured is in the 

 collection of Professor Boettger, of Frankfort, and 

 measures — major diameter, 65 millimetres ; minor 

 diameter, 55 millimetres; altitude, 30 millimetres. 

 A second specimen measures C millimetres in 



diameter. Mr. Gredler, of Bozen, Austria, has 

 obligingly sent to me for inspection two shells of 

 this species which agree with the specimen here 

 figured, except that one has ten instead of eight 

 denticles, in two series of five each. 



Plcctupylis bifoiis (figs 57a-/), from Ta-kouan-tchen, 

 China, was described and figured by Mr. Heude 

 in the second part of his " Notes sur les Mollus- 

 ques Terrestres de la Valle du Fleuve Bleu " (1885), 

 p. Ill, t. 30, f. 2. As I have been unable to obtain 

 specimens of this shell, I have been obliged to rely 

 upon Mr. Heude's description and to copy his 

 figures. The shell is dextral, discoid, plicately 

 striate, brownish, widely umbilicated. The spire is 

 depressed and the apex a little raised. There are 

 six and a-hall slowly increasing whorls, which 

 are flattened above and convex below, the last 

 keeled at the periphery, with a laciniated fringe, 

 and shortly and abruptly descending in front. 

 The aperture is semicircular and the peristome 

 thickened and reflexed, its margins being con- 

 nected by a raised flexuous ridge which 

 is notched at the junction above and below ; 

 about the middle the ridge gives off an entering, 

 flattened fold. The parietal armature consists of 

 two vertical plates united above and below by 

 horizontal folds ; below these occurs a short, free, 

 horizontal fold, while another short, horizontal 

 fold is found aiiteriorly ucar the upper extremity of 

 the vertical plate (see fig. 571?). The palatal 

 armature is composed of four oblique folds, with 

 a fifth smaller one close to the lower suture (see 

 fig. 57^, which gives the anterior view of both 

 armatures). From the figure it appears that there 

 are besides, four small denticles posteriorly to the 

 palatal folds ; but no mention is made of these in 



Fig. ^y.—t'hctopylii bijuris. 

 [After Heudc.) 



the diagnosis (see fig. 57/, which shows the palatal 

 folds and denticles as they appear through the 

 shell-wall). The measurements given are as follows 

 — major diameter, 16 millimetres ; minor diameter, 

 14 millimetres; altitude, 7 millimetres. 

 (To be continued.) 



