ROBERTSON ON THE WEALDEN BEDS OF BRORA. 1 1 ,'5 



Cyclas angulatay Sow., C. subglobosa (sp. nov.), C. lenticularis (sp. 

 nov.), C.rkomboidalis (sp. nov.), C. pr^E-ovata (sp.nov.), C.solidula 

 (sp. nov.), C. unioniformis (sp. nov.), Unio Murchisoni (sp. nov.), 

 and Cypris granulosa, Sow. At the base of this group there is a 

 seam of brownish-grey clay, full of fragments of vertebrata. Among 

 these there are, besides scales of most of the ganoid fishes enumerated 

 above, portions of Emys (?) Oweni (sp. nov.), teeth of Hybodus 

 concinnus (sp. nov.), H. ornatissimus (sp. nov.), H. reticulatus (?), 

 Ag., Acrodus minimus, Ag., and Ctenoptychius (?) Jurassicus (sp. 

 nov.). The total thickness of these strata is 1 ft. 4 inches. 

 /. Fine brown clay with plants. 



The groups c and e appear to be entirely wanting at the Brora 

 Colliery*. This is also the case with respect to the latter at the 

 Water of Brora pitf; but there can be little doubt that No. 37 of 

 that shaft, described as " soft black shale, speckled with white pow- 

 dery matter 2 inches," corresponds to the strata included under c 

 of the coast section ; although neither the vertical distance from the 

 main seam of coal, nor the mineral character of the intervening beds 

 agree at the two localities. 



The Brora Cyclades so much resemble those of some of the 

 Wealden strata of Kent, that, on first meeting with detached frag- 

 ments containing them, I at once conjectured that a contemporary 

 deposit must exist in the vicinity. After finding the beds in situ, 

 however, and tracing them under the coal, (the roof of which Sir R. 

 Murchison had referred to one of the divisions of the middle oolite,) 

 I abandoned my original impression, and was for a time confirmed 

 in the propriety of doing so, when on my return home J failed to 

 identify a single species J with their southern representatives. My 

 esteemed friend Dr. Fleming (at that time personally unacquainted 

 with the geology of Brora) was so struck with the " Wealden aspect" 

 of the shells, as to suggest that the marine bed above might prove to 

 be the equivalent of the lower greensand. This idea 1 knew to be 

 erroneous, and it was not until after a perusal of Sir R. Murchison's 

 observations on the beds now under discussion §, and a subsequent 

 study of the zoological relations which exist between the Wealden 

 above the Portland stone and the various members of the Jurassic 

 series, that I became convinced of the necessity for associating with 

 the former, not only the coal-field of Brora together with certain strata 

 in the vicinity of Elgin and in the Hebrides, but also the carbonife- 

 rous series of the Yorkshire coast, as well as such other similar de- 

 posits, belonging to the same system, as future researches may bring 

 to light. 



At the date of my former communication, I was not aware of 

 the occurrence of freshwater shells in the Jurassic coal-fields of York- 



* Trans. Geol. Soc 2nd Series, vol. ii. p. 326. 



t Op. cit. p. 325. Sir R. Murchison has however reminded me that these sec- 

 tions were made by miners very slightly acquainted with fossils. 



X The specimens of Cyclas angulata. Sow. were obtained during my second visit 

 to Sutherlandshire, and I only recently recognized the Cypris granulosa, Sow. 



§ Proc. Geol. Soc. vol. iv. p. 174. 



I 2 



