cornstone

At the extreme south end, between Kilchattan and Garroch Head, these conglomerates and sandstones are overlaid by a thick cornstone or dolomitic limestone marking the upper limit of the formation, which is surmounted by the cement-stones and contemporaneous lavas of Lower Carboniferous age.

Encyclopaedia Britannica, 11th Edition, Volume 4, Part 4 "Bulgaria" to "Calgary" Various

It is, on the contrary, as a vast amount of various and unequivocal evidence demonstrates, incalculably more modern; nay, we find proof of the fact here in that very bed which has been instanced as rendering it doubtful; the clay of which the interpolation is composed is found to contain fragments, not only of the cornstone on which it rests, but also of the Wealden limestone and shales which it underlies.

The Cruise of the Betsey or, A Summer Ramble Among the Fossiliferous Deposits of the Hebrides. With Rambles of a Geologist or, Ten Thousand Miles Over the Fossiliferous Deposits of Scotland Hugh Miller 1829

The occurrence of the clay here as an inferior bed, with but the cornstone of the Old Red beneath, and all the beds of the Weald resting over it, forms a riddle somewhat difficult of solution; but it is palpably not reading it aright to regard the deposit, with at least one geologist who has written on the subject, as older than the rocks above.

The Cruise of the Betsey or, A Summer Ramble Among the Fossiliferous Deposits of the Hebrides. With Rambles of a Geologist or, Ten Thousand Miles Over the Fossiliferous Deposits of Scotland Hugh Miller 1829