Limestone southward of the Stublick Dike with the northern beds in Northumberland, as the physical characters of the two series are so different, and because, moreover, the organic contents of the southern beds are imperfectly known. In addition to the fossils already noticed I have seen the following, from limestone and shale, at Stanhope: Terebratula hastata; Rhynchonella pleurodon; Athyris ambigua; Spirifer integricostatus, octoplicatus, glaber; Pleurotomaria altavitta; Bellerophon striatus; Dentalium priscum. The beds, in this part of our district, have, however, been divided into two groups; those above the Whin Sill, from the Tyne bottom to the Fell Top Limestone, have been referred to the Yoredale series of Philips, and those below the Sill to the Scar Limestone of that author; but this division seems arbitrary, and is not yet supported by organic remains; and it would moreover apply to a limited area only. It would not apply to the northern series; for the Whin Sill, though intruded into the calcareous division of that group, and generally among the higher beds, has no definite place among them—indeed, it cuts through them, and we find its relative vertical position among the strata varying to the extent of 1000 feet.
Throughout the whole of the Mountain Limestone fossil plants, identical with those found in the Newcastle Coal Measures, or analogous to them, occur in the sandstones and shales, and even in the coal itself. The following species are a few of those which have been noticed: Araucarites carbonarius; Stigmaria ficoides, very abundantly; Sigillaria organa, Lepidodendron Harcourtii, obovatum, aculeatum, Sternbergii, selaginoides, gracile, anglicum, &c.; Ulodendron ornatissimum; Knorria imbricata; taxina; Catamites Suckowii, cannaeformis. &c. Perns, so abundant in the Coal Measures, are rare in this group ; in a few localities Sphenopteris Johnstoniana has been found, a species allied to S. gracilis.
Of our modern Flora a few plants in Northumberland are peculiar to the limestone, such as Sesleria caerulea, Potentilla verna, Spiraea filipendula, and Saxifraga tridactylites. A few others, though not entirely confined to limestone soils, rarely grow elsewhere, such as Scabiosa columbaria, Viola hirta, Plantago media.
