Henry Woodward — Neio British Cystidean. 71 



While the ice was moving forwards, pushing this moraine pro- 

 fonde beneath it, it must have occun-ed that the passage of the 

 moraine over the surface was checked at some points more than 

 others, owing to its being more stony there, or by other causes 

 locally increasing the friction. At such points, the portions behind 

 pressing forward would cause accumulations, which would indent 

 the material into the ground beneath more deeply at those spots, 

 causing those depressions which are so characteristic of the lower 

 surface of the trail. 



The general effect of this action upon the surface of the rock, 

 which had not as yet been actually rubbed off and denuded, would 

 be to drag forward a superficial portion, disturbing it and reducing 

 its thickness ; this effect diminishing downwards, until it disappeared 

 at a depth depending upon local conditions. 



Now when, in this district, the coprolite bed (about a foot or less in 

 average thickness) happened to be near enough to the surface to come 

 within the limit of the disturbed material, on account of its peculiar 

 constitution of small nodules in a soft matrix, it would yield readily 

 to the forward pressure, even more so than the Gault beneath ; but, 

 owing to the nodules, it would be liable to get checked at some 

 points more than at others, and wherever that happened, there accu- 

 mulations would be formed, which would be depressed into the Gault 

 below, and form the pockets which I have described. I may add, 

 that the ridges of Gault between the pockets show surfaces of 

 slickenslide within them, and have small portions of Greensand and 

 phosphatio nodules occasionally impacted into them. 



IV. — Note on a New Bkitish Cystidean. 

 By the Editor. 



IN the Geological Magazine, Yol. VII., p. 260, PL VII... Figs. 

 2-5, we published a description, by Prof, de Koninck, of a new 

 British Cystidean, which the author named Placocystites Forbesianus. 

 We called attention in a footnote (op. cit., p. 261) to the probability 

 of Prof, de Koninck's Cystidean being the same as Mr. Billings's 

 Ateleocystites Huxleyi; but as we had not seen the Canadian specimen 

 upon which the genus was founded, we abstained from speaking 

 very positively as to their identity. We, however, prepared a sketch 

 of Placocystites, which we forwarded by Sir William Logan, who 

 kindly undertook to submit it to Mr. Billings, in order to obtain his 

 opinion thereon. We have been favoured with the subjoined letter, 

 which has, however, been accidentally mislaid, and so for a time 

 delayed in publication, for which we beg to apologize. 



Sir, — Sir W. E. Logan gave me your sketch of Placocystites, 

 and I have this morning re-examined all of our specimens, and 

 also compared Prof, de Koninck's figures and descriptions in the 

 article in the Geol. Mag. to which you refer. Placocystites and 

 Ateleocystites are undoubtedly the same, as suggested by you. 



Anomalocystites, Hall, Pal. N.Y., vol. iii., p. 134:, pi. 7a and 88, is 



