16 FOSSIL ESTHERItE. 



flagstone, slightly micaceous, somewhat varying in tint and hardness. They usually 

 appear to have a superficial smoothness or even gloss, and often a ligbt-brown tint, with 

 some degree of translucency. But the substance of the valve flakes off readily, leaving a 

 film on each of the two surface -planes in a split stone ; and it is comparatively seldom that 

 a valve shows its real exterior ; for, though the surface may sometimes come away from 

 the stone in splitting, and leave a clean cast, yet an outer flake of the valve seems nearly 

 always to have fallen away with the shock of the blow; and the sandy nature of the 

 matrix is too coarse to retain traces of any very fine microscopic sculpturing in the cast or 

 mould of the surface. Something like a regular sculpturing appears on some specimens, 

 as we see in fig. 5 ; but this is too much interfered with by the pressure of the sand- 

 grains to be taken for the true ornament. 



In the Kirkwall specimen the valves are pyritized ; but those from Caithness retain 

 their brown horny tissue, although the outermost surface is seldom preserved, and only in 

 little patches on some valves. Erom this circumstance it is very difficult to form a correct 

 diagnosis of the species ; for the superficial ornamentation yields important specific cha- 

 racters in this genus, and in this case it cannot be satisfactorily studied. 



Mr. C. W. Peach, of Wick, has favoured me, at my request, with the following notes 

 on the geological distribution of the Estheria membbanacea : — 



" The first place where they were discovered was Pickoquoy Quarry, near the Peerie 

 (Little) Sea, at Kirkwall. I have got them there in situ. They are found in a thin bed,-^ 

 and lie in great quantities on the surface-planes, never to any depth, but just, as it were, 

 interleaved. Here, as well as at all the other localities, they are accompanied by scales of 

 fish and pieces of bone (of Dipterus, &c.). 



" They occur also at Marwick Head, near Skaill, Orkney ; and Avere found there first 

 by Mr. W. Watt. In 1857, 1 found them in a new locality in Orkney, at the farm of 

 Churaley, between the manse of Sandwick and Stromness, in a small quarry opened to 

 build the farm-house and buildings there. The matrix is coarse, rather soft, and pale-blue, 

 but makes good building-stone. They were rare, and were accompanied with a few fish- 

 scales, probably of Dipterus. 



"At Thurso East, Mr. Dick has got them near the castle-residence of Sir George 

 Sinclair, Bart. I have also seen them in situ there, but few fell to my lot. I saw por- 

 tions of fish remains near them. Mr. Dick has also got them in great quantities at Murkle 

 Bay, between Thurso and Castle Hill. 



" At Castle Hill, under the house of Mr. Traill, M.P., they are very abundant (first 

 found by Dr. Sutherland), in a good building-stone, of a similar colour to that of Thurso 

 and Chumley — pale-blue, and soft to the touch ; as also at Kirkwall, &c. At Castle Hill 

 they are not in thick layers, but interleaved, and occur with Eish-remains and Coprolites, 

 lying amongst and on them. Near this place, about 10 feet above the Estheria-beds, are 



1 Scarcely half an inch in thickness, according to Hugh Miller ; see his description of the quarry, 

 in 'The Cruise of the Betsey,' 1858, p. 415. 



