Clifton College Scientific Society. 1 7 



Davidson, who wrote after M'Coy, remarks that the three latter 

 difierences are miimportant, considering how much S. crenistria 

 varies in these respects. You will easily see this in the specimens 

 from the Black Eock, one very small one having very acute car- 

 dinal angles. 



With regard to the second point, he shows that S. crenistria 

 has its angles sometimes acute, sometimes rounded, as you will 

 see by comparing the sketches and specimens from the Black 

 Eock. Still no specimen had as yet been found with the mesial 

 furrow, and also with its cardinal angles acute ; so although he 

 thinks S. Kellii is only a variety of Crenistria, he leaves the 

 question open, putting a note of interrogation after the words 

 ' this species or variety.' 



The shell marked No. 3 supplies this want ; it has the furrow 

 and also the acute angles. There is then only the furrow left. 

 The specimens from the gully vary very much in the depth of this 

 furrow, and in some it is almost obliterated. These shells then 

 form the connecting links between Kellii and Crenistria, and we 

 may safely conclude that the former is only a variety and not a 

 separate species. 



The Peesident then read the following paper on the Lower 

 portion of the 



LOWER LIMESTONE SHALES, CLIFTON. 



The Carboniferous Limestone near Bristol, as exposed in the 

 section of the river Avon, is separated from the Devonian or Old 

 Eed Sandstone by a series of beds of shale alternating with thin 

 bands of limestone. The Carboniferous Limestone extends from 

 the St Vincent Eocks to the Black Eock, and the shales extend as 

 far as Cook's Folly, where they are replaced by beds of dark red 

 sandstones, grits, and marls. The thickness of the limestone is 

 given as about 1450, and that of the shales as 500 feet. Towards 

 the lower part of the shales is the celebrated Clifton bone bed, 

 which is full of coprolites, and contains many fish teeth. 



This bed is rather more than 100 feet above the Old Eed Sand- 

 stone. It was at one time looked upon as the base of the Lower 

 Limestone shales. In the first volume of the Geological Society's 

 Memoirs is a detailed description of the Avon section, including 

 these beds, by Mr Williams of the Geological Survey. He found 

 fossils in only one bed below the bone bed, at a distance of about 

 6& feet from it. Mr Stoddart subsequently found that some beds 

 immediately below the bone bed were composed mainly of fossils 

 called Bryozoa, and a little further down, 24 feet below the bone 



B 



