Post-Tertiary Deposits of the Basin of the Clyde. 155 



undiscovered ; and for others being varieties of those which are. Had I in- 

 cluded them all, the proportion would be nearly 20 per cent. Upon separating 

 the fossil catalogue, in my paper in the Memoirs of the Wernerian Society, 

 vol. viii., into what I consider tertiary and post-tertiary species, I find the num- 

 ber of the former 151, of which 27 species are unknown as British. 



The researches of the Rev. David Landsborough, in the summer of 1840, fully confirm the existence of 

 two separate epochs in the elevated marine beds, which are newer than the till or diluvium. At Steven- 

 ston in Ayrshire he found, at the depth of thirty-five feet under the surface, a bed of blue clay, with 

 newer Pliocene shells : out of twenty-seven species, there were eight of them extinct or unknown. In a 

 superficial raised beach, in the same parish, he found forty -seven species, all recent ; and in another at 

 Largs, in the same county, sixty-eight species occur. 



It is remarkable that none of the fossils of the older of these beds have been yet found mixed up with 

 those of the newer or raised beaches. (May 1841.) 



1. Tellina proximo, Wern. Mem., vol. viii. p. 105, PI. I. f. 21. — Closely allied to the T. prcetenuis, a 



crag fossil. It has been discovered in a recent state in the Arctic seas, beyond Behring's Strait, 

 by Capt. Beechy, and fossil at Udevalla. 



2. Crassina multicostata, Wern. Mem., vol. viii. p. 104, PI. I. f. 20 ; Phil. Trans. 1835, PI. II. f. 21.— 



It resembles the C. compressa, a recent species, but is less regularly striated. M. Deshayes 

 says that it is recent in Norway and Sweden ; Mr. Lyell found it in a fossil state at Udevalla ; 

 and Mr. Muichison. in Russia. (1840.) 



3. Crassina propinqua, nearly related to the last, but with a much thicker hinge (1841). 



4. Crassina Withami, Wern. Mem., vol. viii. p. 105, PI. I. f. 25. — Found by Mr. Witham in a fossil 



state at Bridlington, and by Mr. Forbes at Wick ; a single valve was dredged by Mr. Sowerby 

 and me in Rothsay Bay : it is perhaps, therefore, a recent shell, but as the newer Pliocene de- 

 posit passes below the sea at Bute, this is not a conclusive proof that it is so. 



5. Crassina borealis, Chemnitz, vol. vii. p. 26, PI. XXXIX. f. 412. — Recent in the North Sea, fossil 



in the upper crag. 



6. Mya . Closely allied to M. truncata, but differing so constantly in the muscular impres- 



sion that Mr. G. Sowerby considers it a separate species. Found fossil by Mr. Lyell at Udevalla. 



7. Pecten Islandicus, Brown's Illust., PI. XXXIII. f. S — Although this shell appears in the works of Tur- 



ton, Fleming, and Brown, as a recent British species, I am satisfied, from the localities given, 

 that the specimens described were from the ancient beds in which it is very abundant, and that 

 it has not hitherto been found in a living state in our seas ; it occurs recent in the North Sea 

 and at Newfoundland, and fossil at Udevalla. 



8. Nucula oblonga. — This shell also appears in Brown's Illustrations, PI. XXV. f. 17, but as it is from 



a locality whence these fossils are abundant, and as it has not been found since in a recent state, 

 it is probably one of them ; it resembles the N. minuta, but is larger and not transversely stri- 

 ated. Mr. Gray considers it an Arctic shell. Found fossil by Mr. E. Forbes in the Isle of Man, 

 by Capt. Portlock in Ireland, at an elevation of 400 feet, and by Mr. Murchison in Russia. 



9. Nucula antiqua. — This shell is transversely striated, and is higher in proportion to its breadth than 



the N. oblonga. 



10. Nucula pygmcea, Goldfuss, PI. CXXV. f. 17 ; Wern. Mem., vol. viii. p. 107, PI. II. f. 10; Philippi 



Mollusc. Sicil., PI. V. f. 9. In the catalogue in the Wernerian Memoirs it is named N.gibbosa, 

 but is undoubtedly the N. pygmcea of Goldfuss, a fossil from Mechlenburg. Mr. Lyell found 

 it in an elevated deposit at Dundee ; Mr. S. Wood in the crag, see his Catalogue, Nat. Hist. 

 Mag., 1840, p. 298. It agrees also with the Sicilian fossil figured and described by Philippi. 



11. Cytherea Icevigata, — A small but very distinct species (1841). 



x2 



