SCIENCE-GOSSIP. 



276 



Plectopylis affinis (i) (figs. j,\a-d), from the Khasia 

 Hills, has hitherto been confused with Plectopylis 

 phctostoma, but it differs in being larger and much 

 paler in colour, in having four instead of five rows 

 of hairs, which are not placed on raised ridges as in 



c d 



Fig. 41. — P!ecfopylis affinis. 



that species ; the cuticle is much thinner and not 

 plaited, while the spiral sculpture is less coarse 

 above and scarcely perceptible below, where the 

 shell is also more shining than in P. phctostoma. 

 The shell is translucent and the armature is 

 distinctly visible through its wall, while the 

 aperture is more narrowed laterally and the upper 

 margin of the peristome is less arcuate, being a 

 little inflected. The umbilicus is also wider and 

 scarcely angulated, while the base is much more 

 flattened. The ridge of the parietal callus is 

 more raised and more curved. The parietal 

 armature consists of a vertical plate with 

 a very short support anteriorly at the upper and 

 lower extremities, but without the horizontal fold 

 above as in P. plectostoma. The two denticles on 

 the posterior side are larger and more elongated, 

 and below the vertical plate are two short, thin, 

 horizontal folds in a line with each other (see 

 fig. ^id, which shows the parietal wall by itself; 

 and fig. 4if, which shows both armatures from the 



posterior side). The palatal armature is similar to 

 that of P. plectostoma, but the posterior portions of 

 the third, fourth and fifth folds, instead of being 

 straight and almost vertical, are crescent -shaped 

 and oblique (see fig. 41&, which shows the palatal 

 folds as they appear through the shell-wall) ; an 

 additional semi-circular fold, posterior to but a 

 little above the fifth fold, occurs in this specimen ; 

 this, however, I have not observed in any of the 

 other specimens. Fig 41a shows the entire shell 

 enlarged. My specimens were obtained from Mr. 

 Fulton some years ago ; the twenty-five further 

 specimens from the same locality, sent to me for 

 inspection by him, range from g to 11 millimetres in 

 diameter. Two immature specimens in my collec- 

 tion are composed of five and a-half whorls ; one of 

 these has the immature barriers complete, but the 

 palatal folds are very short and the posterior oblique 

 portions of the fourth and fifth folds are almost 

 straight instead of crescent-shaped ; externally a 

 slight trace of previous folds can be discerned ; in 

 the other specimen the last immature folds are 

 similar to those of the first specimen, but the 

 remains of a previous set is in a less advanced 

 stage of disintegration. 



(To be continual.) 



(•) Pkctopyl's affinis. n. sp. (figs. 4i«-rf).— Shell sinistral, 

 somewhat widely umbilicated, dis-k-shaped, pale vellowisit 

 corneous, tranihtcent, radiately plicate, decussated by spiral 

 lines above, smoother and shining below. Whorls 7, nar- 

 row, increasing slowly, the last Xi'idening towards the 

 aperture, and descending a little in front, rounded above, 

 flattened below ; Jour lines of soft pilose hairs pass round 

 the whole length of the body whorl, the first on the angulated 

 periphery, the second a little below it, the third midway 

 between the second and fourth, which is near the umbilicus. 

 Aperture ear-shaped, elongated vertically ; peristome white, 

 thickened and leflexed, upper margin a little depressed ; the 

 raised//f.v«o;is ridge on the parietal callus is separated from the 

 margins by a slight notch. Umbilicus deep and moderately 

 wide. The parietal armature consists of a vertical plate witli 

 two short supports anteriorly, one above and one below, 

 and two elongated denticles posteriorly, one above and one 

 below ; two free, short, horizontal folds in a line occur below 

 the vertical plate. The palatal armature is composed of six 

 folds, the first and sixth short, thin and horizontal, the 

 others longer and broader ; the second a little indented in 

 the middle, with the posterior termination raised obliquely; 

 the third is notched in the middle, and deflects obliquely 

 posteriorly ; the fourth and fifth are in two series separated 

 by a short space, the anterior portion straight and hori- 

 zontal, the posterior portion crescent-shaped and obliquely 

 descending.— Major diameter, iomillimetres;minordiameter, 

 9 millimetres; axis, 5-5 millimetres.— Habitat, Khasia Hills, 

 Assam. — Type in my collection. 



