ftS Professor E. Forbes on the Oolite in Skye. 



water 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 dis- 

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

 fossils known to me and not published. Both the identifica- 

 tions 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 al- 

 together 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 this paper will now 

 hold. The comparison and determination of freshwater 

 bivalves is a matter of great delicacy and practice ; the dis- 

 tinctions between the species of Cycladidce and Unionidce re- 

 spectively being of so delicate a character that the examina- 

 tion of numerous specimens of each species is necessary, 

 combined with a knowledge of the recent species of these ex- 

 cessively difficult tribes. I cannot satisfy myself that any 

 one of the Loch Staffin shells is identical with a Purbeck or 

 Wealden species. This, in the present state of our know- 

 ledge, was to be expected. 



A more curious result is that, after a close comparison of 

 both Sir Roderick's and my own specimens (now contained 

 in the collection of the Museum of Practical Geology), I can- 

 not satisfy myself that, with the exception of the Faludina 

 conulus of Robertson, which is a little Hydrobia identical with 

 the unfigured Paludina mentioned in Sir Roderick Murchison's 

 Loch Staffin list, there is any one of the Loch Staffin estuary 

 shells identical with a Brora species. The little Hydrobia 

 above mentioned, however, appears to be undistinguishable. 



The succession of events indicated by the section I have 



