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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[Mar. 6, 



oolitic and polyzoan limestone, from which I obtained an interesting- 

 suite of fossils. The common fossil is a Polyzoon — Acantliocladia 

 anceps. The associated species, among which are those mentioned as 

 the common fossils of other localities, are all of subordinate importance 

 in respect to individual distribution. Besides the species of Polyzoa 

 named, three others have occurred to me in the polyzoan beds, two of 

 which (Retepora Ehrenbergi and Thamniscus dubius) are peculiar to 

 it. The beds in which the Polyzoa are so profusely distributed 

 scarcely ever contain species belonging to other classes. 



I chiefly notice these fossiliferous localities in detail to draw some 

 attention to the manner in which different species characterize certain 

 localities. In some cases this seems to be due to the localities repre- 

 senting different horizons of the Lower Limestone, consequently differ- 

 ent periods of Permian time, which in this area were characterized 

 by the prevalence of different common species. This is certainly 

 the case with the Moorhouse and BrodsAvorth localities, whose 

 vertical position in the series it is not difficult to test, the former 

 evidently underlying the latter. In other instances the differences 

 observed appear to be merely those of geographical distribution ; 

 as, for example, that of Hanipole and the Freestone Quarry 

 near Pickburn, the beds of both appearing to be of the same relative 

 position. To the palaeontologist these groups of species and their 

 differences are of particular importance — just as much, perhaps, as 

 the larger groups (and their differences) belonging to different 

 formations of strata : for, as the one tells of great and wide- 

 spread changes in the relations of ancient life during the elapse of 

 immense ages, so does the other of the small and limited changes 

 which happened during shorter periods, and from which the first 

 eventuate. 



The species that are found furthest down in the Lower Limestone 

 are Axinus dubius and QerviUia antiqua. Casts of these shells 

 (those of the former being most prevalent) occur in the lowest beds of 

 compact and earthy limestones immediately above the llothliegendcs 

 at Carlton, Wentbridge, and Pontefract (Bagg Hill). Other species 

 soon appear in the beds that follow ; but for some feet upwards 

 Aocinus dubius holds its own, and increases in size and numbers, 

 until it attains its maximum in certain strata, not so very far above 

 the sandstone as at Moorhouse and Conisborough. In the succeeding 

 beds GervUlia antiqua becomes very numerous and takes the place of 

 the other as common species. Near about the same horizon as the 

 latter, or possibly a little below it, are the beds in which Acantliocladia 

 anceps is so common in the region between the Don and the Went. 

 Above these beds and in the highest portion of the member, fossils 

 become rarer, and the species that occur are more equally represented. 



The assemblage of fossils at Hampole is, perhaps, the most curious 

 of any that occurred to me in South Yorkshire. As already remarked, 

 it is chiefly composed of Univalves, all of which are minute, their 

 small size being due in the case of Turbo helieinus, Turritella Alt-en- 

 burgensis, and one or two others, to the immature condition of the 

 specimens, which are invariably young and somewhat dwarfed 



