414 



J. W. DAVIS OK THE FISH-REMAINS OF 



32. Notes on the Eish-remains of the Bone-bed at Aust, near 

 Bristol ; with the Description of some new Genera and 

 Species. By James W. Davis, Esq., F.G.S. &c, Hon. Secretary 

 of the Yorkshire Geological Society. (Bead May 11, 1881.) 



[Plate XXII.] 



I am indebted for the material on which the following paper is. 

 based to Mr. "W. T. Ord, of Bristol, to the Council of the Geolo- 

 gical Society at London, who have kindly placed their collection at 

 my disposal, and to Mr. Sollas, Professor of Geology at the 

 University College, Bristol. 



The specimens are in good preservation, the smaller ones, con- 

 sisting principally of teeth, being unbroken ; the larger bones, as 

 for example, ribs or other bones of Saurians, the larger spines of 

 Eishes, &c, are generally found in a more or less fragmentary and 

 broken condition. 



From the occurrence of the teeth which are characteristic of the 

 older Carboniferous rocks, such as Psammodus joorosus, Helodus, 

 and Psephodus magnus of the Mountain Limestone, and Cteno- 

 ptychius, which has hitherto been found in the Carboniferous 

 series, and more especially in the Coal-measures, it appears pro- 

 bable that some of the fossil remains found in the Rhastic beds at 

 Aust have been derived from the disintegration of the older rocks. 

 Either this must have been the case, or the genera of fishes named 

 had a considerably longer period of existence than has hitherto 

 been supposed. It may be objected that the remains are in a very 

 perfect state of preservation (as, indeed, they are in most cases) and 

 do not appear to have been exposed to much attrition by being 

 washed on the shore or bed of the sea or a lake. It is probable, 

 however, that the area over which the bone-bed was deposited was 

 composed, in the neighbourhood of Aust at any rate, of the blue 

 clays which at present underlie it. During the formation of the 

 bone-bed the nodular masses of blue-grey stone which are now 

 found composing a great proportion of its mass were pieces of 

 clay, rolled round by the action of the waves or tides, so soft that 

 they received easily an impression of the bones or teeth which lay 

 scattered along the shore with them. Erom the immense number 

 of fossil remains of Saurians and Eish which occur in the bed, it will 

 be inferred that it required a long period of time for their accumu- 

 lation, and that throughout all that time there was a peculiar absence 

 of sedimentary deposits, the nodular masses being derived from the 

 adjoining Keuper beds, which also formed the floor on which the 

 bone-bed was deposited. 



In a paper read to this Society in 1841 * Mr. Strickland showed 

 the bone-bed to extend over a surface of 120 miles ; and since that 



* Proc. Geol. Soc. vol. iii. part ii. p. 585. 



