546 E. M. Kindle—Pit and Mound Structure. 
concretions' in the Potsdam sandstone near Kingston might be 
developed. 
[ Norr.—Fig. 2 (added by the Editor to this Plate) has been repro- 
duced from a photograph faken direct, by the kind permission of 
Dr. A. Smith Woodward, the Keeper of the Geological Department of 
the British Museum (Natural History), Cromwell Road, London, 
from one of the original dried slabs of reddish mud, presented 
by Sir Charles Lyell from the Bay of Fundy, Nova Scotia, 
which are still carefully preserved in the Geological Gallery, 
and were described by Lyell in his paper ‘“‘On Fossil Rain- 
marks of Recent ‘Triassic and Carboniferous Periods’, April 30, 
1851 (see Quart. Journ. Geol. Soe., vol. vii, pp. 288-47. See also 
woodcut, p. 240), where he writes: ‘‘The finest examples sent to 
me from Kentville (Bay of Fundy) were made by a heavy shower 
which fell on July 21, 1849, when the rise and fall of the tides were 
at their maximum in that small estuary which opens into the Basin 
of Mines. The impressions [see owr reproduction Pl. XIII, Fig. 2] 
consist of cup-shaped or hemispherical cavities, the largest being 
fully half an inch in diameter, and from one-tenth to one-sixth of 
an inch deep; but there are very few of such dimensions. The 
depth is chiefly below the general plane of stratification, but the walls 
of the cavity consist partly of a prominent rim of sandy mud, formed 
of the matter which has been forcibly expelled from the pit, and this 
margin or lip sometimes projects as much above the plane of the 
stratum as the bottom of the pit extends below it. The rim of the 
largest rain-prints is sometimes no less than one-twelfth of an inch 
broad, but it is usually much narrower. ‘The outer side of it is often 
perpendicular or almost overhanging. . . . All the cavities having 
an elliptical form are deeper at one end, where they have also 
ahigher rim, and all the deep ends have the same direction showing 
towards which quarter the wind was blowing. Two or more drops 
are sometimes seen to have interfered with each other, in which case 
it is usually possible to determine which drop fell last, its rim being 
unbroken. ... ” Lyell adds a note to his paper: ‘‘ Since the above 
was in type, my attention has been called toa notice by Dr. Buckland? 
‘On Cavities caused by Air Bubbles on the Surface of Soft Clay’, 
which he justly observed ‘must be carefully distinguished from 
impressions made by rain’ ”’. 
As bearing upon the present paper, we may draw attention to 
a Plate (Pl. IV, Vol. II, Guor. Mac., 1865, p. 137), reproduction of 
markings on the surface of a. slab of Carboniferous Sandstone 
from Bishop Auckland, described by Mr. J. Duff. Also suggested. 
explanation by Mr. Alexander Bryson, accompanied by a text- 
diagram figure (Grot. Mac., 1865, pp. 188-91), in which the writer 
shows that these horseshoe-like markings are in.all probability to be 
attributed to the heaping up of grains of sand against the windward 
side of the burrows of the common sandhopper ( Zalitrus saltator), the 
1 N.Y. State Mus. Bull. 145, pl. xiii. 
* Reports of British Association, 1842, Trans. Sect., p. 57. 
