in the CanneUcoal of Fifesldre* 315 



geological history of the Purbeck series, is the occurrence of a 

 bed of oyster-shells, called the cinder-bed," often many feet in 

 thickness, and almost wholly composed of dark-coloured small 

 oyster-shells in the midst of a series of strata, some of which 

 contain exclusively shells of fresh-water formation, and others an 

 admixture of fresh-water shells with those which are marine; 

 and although we cannot infer from it the return of the sea for 

 any long period in the middle of the Purbeck formation, yet it 

 shews that the district it occupies could not have been a lake of 

 pure fresh water, but was probably an estuary at the time when 

 these oysters occupied its bottom, and were accumulated to the 

 thickness of many feet over a distance of many miles."" The 

 same authors add a note descriptive of the Lake Menzale, at the 

 mouth of the Nile, which, they remark, " is highly illustrative of 

 the mode in which living animals, of a mixed character, are as- 

 sociated together near the confluence of great rivers with the sea.'" 

 2^/7/, As to the plants. All the species of plants which have 

 been found in this limestone have been met with in the shales 

 and sandstones of other coal-fields, either of this country or of 

 the Continent. The Sphenopteris affinis which, as Dr Hibbert 

 states, occurs in greatest abundance in the limestone, is com- 

 mon in the roof of the Benshara coal-main in Jarrow colliery, 

 near Newcastle;* and the Lepidostrobus variabilis, of which a spe- 

 cimen from the limestone is figured by Dr Hibbert, associated 

 with a fish of the genus Palasoniscus, which I shall afterwards 

 shew must have lived in the sea, is also met with in Jarrow col- 

 liery .-f- But these plants are not confined to the coal-measures ; 

 but are met with throughout the whole carboniferous series, 

 from the old red to the new red sandstone. M. Elie de Beau- 

 mount describes the graywacke rocks, at the extremity of the 

 Vosges Mountains in Alsace, and of the Bocage in the depart- 

 ment of Calvados, a part of ancient Normandy, as containing 

 vegetable impressions scarcely differing from those found in the 

 coal-formations. J They are by no means uncommon in the car- 

 boniferous limestone ; and I have seen in the collection of Pro- 

 fessor Jameson, specimens collected by him near Pettycur in 

 Fifeshire, of a coarse limestone belonging to the coal-measures 



• Fossil Flora of Great Britain, plate 45. f Ibid, plates 10 and 11. 



X Phil. Mag. and An. vol. x, p. 247. 



