﻿1851.] 



FORBES ON THE OOLITES IN SKYE. 



107 



1 1 . Soft white sands with traces of bivalve shells, apparently Cy- 

 rence, 3 feet. 



12. Hard sandstones with Perna and numerous Ostrece and Cy- 

 rence, 2 feet. 



13. Greyish sands with carbonaceous streaks and lenticular courses 

 of comminuted shells ; concretions in places ; 5 feet. 



14. Hard calcareous shales with bands of Cyrence and fossil wood, 

 3 feet. 



15. About fourteen bands of loose calcareous slaty and shaly beds 

 filled with Cyrence, occasional Uniones, and OstretB : these appear to 

 constitute a thickness of about 1 2 feet, but the base of them resting 

 on the basalt is concealed under water. 



The dykes of trap in communication with the superincumbent 

 amygdaloid bake the strata through which they pass and alter the 

 mineral character of the fossils. 



The position of these estuary beds, beneath the Oxford clay and 

 above the mass of the middle oolites, at once removes them from 

 identification with Wealden or tertiary strata of the South of England, 

 and as readily suggests a comparison of them with the so-called 

 "Wealden beds," discovered by Mr. Alexander Robertson, interca- 

 lated with the carboniferous portion of the oolitic strata of Brora in 

 Sutherlandshire, and described by that gentleman in two most inter- 

 esting papers communicated to the Geological Society in 1843 and 

 1846. The main seam of Brora coal lies immediately beneath a 

 stratum containing Kelloways Rock fossils, and regarded by Sir 

 Roderick Murchison as the representative of the pier stone of Scar- 

 borough. Below the coal beds are bituminous shales, clays, and a thin 

 layer of whitish argillaceous limestone, containing numerous remains 

 of Fish, and of shells of the genera Cyclas or Cyrena, Unto, Perna, 

 Tellina, and Paludina. These shales are superior to the oolitic and 

 liassic strata. 



Mr. Robertson enumerates the many fossils found by him, but 

 does not describe or figure the new species. Of the freshwater or 

 estuary invertebrata found by him in the Brora strata, only two are 

 mentioned as identical with known species, viz. Cyclas angulata, 

 identified with a Wealden shell, and Cypris granulosa, considered 

 the same as a Wealden crustacean. Mr. Robertson presented the 

 best specimens of all his species to the Geological Society, where I 

 have had an opportunity of inspecting them, and can speak to their 

 distinctness from known forms, or from any of the many Purbeck 

 fossils known to me and not published. Both the identifications 

 above mentioned I consider to be insufficient. The Cyclas, called 

 angulata, from Brora is not to me identical with Sowerby's shell, 

 and the Cypris referred to granulosa is altogether distinct. 



Through the kindness of Sir Roderick Murchison, I have had an 

 opportunity of comparing his original Loch Staffin fossils with those 

 collected by myself. He procured two with which I did not meet, 

 and I found some additional to his. None of the identifications in 

 the list appended to his paper will now hold. The comparison and 

 determination of freshwater bivalves is a matter of great delicacy and 



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