644 FOURTH RKPonx — 1834. 



The limestone quarry of Burdiehouse was very briefly de- 

 scribed, as many details regarding it have already been published 

 by the author. This limestone is a very deep-seated bed in the 

 carboniferous series. Above it are alternating beds of sand- 

 stone, shale, and thin seams of coal. A limestone contain- 

 ing marine shells and corallines follows, while the whole is 

 surmounted by the coal-measures of Loanhead. The Burdie- 

 house limestone incloses a variety of plants, minute Entomo- 

 straca (among which there appears to be a Cypris), various un- 

 described fish, the bones of gigantic animals, large scales, and 

 coprolites. Among the bones are pointed teeth of the extraor- 

 dinary length of three inches and three quarters, and of the width 

 of one inch and a half at their base, wliich resemble those of 

 Saurian reptiles. These teeth are adorned with a most beau- 

 tiful brown enamel, as well as the large scales which are so 

 plentifully found in the quarry. There were also exhibited some 

 bony rays of the extraordinary length of fifteen inches, which 

 must have belonged to an immense fish. 



The author announced that all the relics of fish hitherto dis- 

 covered at Burdiehouse would be submitted to the inspection 

 of M. Agassiz, who, in the invaluable work on fossil ichthyology 

 which he was publishing, promised to fill up, with the success of 

 a Cuvier, this great blank in natural history*. 



On the Geological Structure of the Orkney Islands. By 

 J. S.Traill, 3I.D. 



The geological character of these islands is very simple ; the 

 whole group, with the exception of a small granitic district near 

 Stromness, consisting of rocks belonging to the old red sand- 

 stone formation. The prevailing rock is a species of sandstone 

 flag, much charged with argillaceous matter. It occurs in di- 

 stinct strata, usually slightly inclined, which form hills of but 

 small elevation, but often present very magnificent cliffs around 

 the coasts. It has a colour varying from pale greenish to 

 blackish grey. It has a slaty structure, and readily splits into 

 layers, the thickest of which form a very durable building-stone, 

 as the remains of very ancient Scandinavian edificies attest ; 

 while the thinnest form excellent flags, or even a tolerable roof- 

 ing-slate. It is in this slaty rock that the fossil fishes are found. 

 It occasionally contains bitumen, so as in a few places, espe- 

 cially in the islet of Rushholm, to approach to bituminous 

 shale. 



* Dr. Hibbert likewise displayed the teeth and other relics of a large fish, 

 which he had recently discovered in the black limestone of Ashford,-in Derby- 

 shire. 



