MEDINA SANDSTONE. 
53 
The figure No. 10 is a representation of a small specimen with three shells of the Lingula 
cuneata, each with the little ridge of stony matter as described, extending from its beak. It 
will be recollected, also, that it is not to the surface of a single layer or stratum that these 
shells are confined. They appear upon successive strata for many feet in thickness, and they 
are sometimes separated from each other by a deposit of less than half an inch. These cir¬ 
cumstances prove the operation of similar causes during a long period of time. Each suc¬ 
ceeding layer retains the impressions in a very beautiful manner, and thus we often obtain 
specimens with shells upon the upper side, and casts upon the side below. Several large 
slabs of this kind may be seen in the State collection. 
The evidence from these drifted shells, with their ridges of stony matter, corroborates the 
inference drawn from the condition of the fossils at Medina. It will be noticed, also, that the 
position of the fossils at the latter place is east a little south from the quarries near Lockport, 
of which we have been speaking. The direction of the current as there indicated would have 
a tendency to drift all the shells in a south and easterly direction. Since this mass has once 
extended much farther north than at present, as is evident from its abrupt outcrop, and the 
great excavation of the lake valley, it is quite probable that Medina was brought within the 
range of the current from the N.N.W., and that from the proximity of land or very shallow 
water, the fossils accumulated as there described. 
The Lingulae are not alone in the production of these appearances upon the surface; in 
some instances we find small fragments or pebbles of a greenish shaly sandstone, precisely 
like some parts of the lower mass, which seem to have been stranded in like manner as the 
shells. This is seen in the specimen of which Plate II. is a representation. In this instance 
three of the largest obstacles are fragments of green shaly sandstone, and the others shells 
of the Lingula. 
It might appear from what is here stated, that there is a discrepancy in the direction of the 
water as indicated by the Lingulas, the little ridge of sand pointing northwardly, while the 
fossils are accumulated in a southeasterly direction. The explanation seems to me to be this, 
though some other view may be adopted : The surface on which the shells were stranded, was 
a long low beach or sandbar washed by the waves of the ocean, as will be seen by further 
illustration. The shells were carried forward by the waves, which advanced high up the 
beach ; with the retiring wave, all these would be moved backward a short distance, but would 
soon be left attached to the sand, the water of the still retiring wave scooping out the depres¬ 
sion in front and at the side, and piling up the little ridge beyond the beak. In this manner, 
the direction apparently indicated is opposite the real direction of the force which transported 
the specimens. That such is the process by which shells and pebbles are stranded on the 
present beaches, any one will be convinced by observation. By the retiring of the wave, also, 
any single valve of a bivalve shell, which may remain with the outer side downwards, will 
surely be overturned, and at last usually remain in the reverse position, as is the case with 
all the shells of the Lingula on the sandstone. After being once fixed in this manner, they 
are not easily removed by succeeding waves. 
The surfaces of these slabs upon which the shells are found have often a beautiful clouded 
