276 



SCIEXCE-GOSSIP. 



PUcicpylis affinis {}) (figs. 4i<7-i). from the Khasia 

 Hills, has hitherto been confused with Plectcfylis 

 pUctostoma, 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 



F:g. 41. — Pleciopylh 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 narrovred 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 mere 

 flattened. The ridge of the parietal callus is 

 more raised and more curved. The parietal 

 armature consists of a vertical plate v.ith 

 a very short support anteriorly at the upper and 

 lower extremities, but v.ithout 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. 4i(f, which shows the parietal wall by itself; 

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



(I) PUctopyl's afftnis, n. sp. (figs. iIa-<f^— Shell sinistral, 

 somewhat uidely umbilicated, disk-shaped, pale yellowish 

 corneous, translucent, radiately plicate, decussated by spiral 

 lines above, smoother and shining belou:. Whorls 7, nar- 

 row, increasing slowly, the last widening towards the 

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

 flattened below ; four 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 reflexed, upper margin a little depressed ; the 

 raised /i?j:i«>«s ridge on the parietal callus is separated from the 

 margins by a slight notch. Umbilicus deep and moderately 

 •.ride. The parietal armature consists of a vertical plate with 

 two short supports anteriorly, one above and one below, 

 and two elongated denticles posteriorly, one above and one 

 below : teo 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, 10 millimetres ; minor diameter, 

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

 Assam.— Type in my collection. 



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. 4iZ>, 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 9 to 1 1 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 continued.) 



Oldhavex Beds. — Mr. William Whitaker first 

 proposed, in 1866, the name of Oldhaven (and 

 Blackheath) Beds for those singular accumulations 

 of pebble-beds which occur between the London 

 clay and the Woohvich and Reading beds, and 

 which had previously been classed by Professor 

 PrestW'ich as the basement -bed of the London 

 clay. The pebble -beds are easily recognized 

 in consequence of the well-worn condition in 

 v.hich the pebbles are left after deposition. As an 

 explanation of the fact that there is rareh' any- 

 thing lite a sub-angular flint to be seen in these 

 beds, " one is led to infer that they must have been 

 deposited some way off the shore, as a bank to 

 which no flints could get until after having been 

 long exposed to wearing action." This method of 

 their origin has been repeated in various books on 

 the subject, but it does not seem to me that it 

 altogether satisfactorily accounts for the presence 

 of vegetable remains that are occasionally found in 

 the mass of pebbles. Last year I saw a layer of 

 about six inches of peaty matter intercalated 

 between identical pebble-beds, all resting upon 

 Woolwich beds. I further observed Melania in- 

 quinaia and Cyrena flumenalis , in a smaller pit at 

 Charlton, just east of the road leading from Lower 

 Road up to Charlton Church. The oscillations 

 of surface which Mr. Whitaker thinks may have 

 marked the period I would suggest may in this 

 case have actually brought the sea-bottom above 

 the sea-level, and caused a growth of vegetation 

 that was afterwards thrown down bj- the incoming 

 sea on the subsidence of the area. — Edziard A . 

 Martin, 69, Bensham Manor Road, Thornton Heath. 



