Definition of "lissen"

And I remember in my youth, in the Lisne of a Rock at Kingſcote in Gloceſtershire, I found at least a Bushel of Petrified Cockles actually distinct one from another, each near as big as my Fist.

a. 1677 (date written), Matthew Hale, The Primitive Origination of Mankind, Considered and Examined According to the Light of Nature, London: […] William Godbid, for William Shrowsbery, […], published 1677

Beside these, we have another fine Earth, of a white co­lour, porous and friable, insipid and without scent, dissoluble in water; and tinging it, of a milky colour, and somtimes raising a kind of ebullition in it; found frequently in the lissoms or seams of the Rocks, or sticking to the hollow roofs of them: in short, so altogether agreeable to what Conradus Gesner calls Lac Lunae, that I could not but think it the very same.

1677, Robert Plot, The natural history of Oxford-shire