Page:Transactions of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne (1867).djvu/26

10 interstrialis; Amusium Sowerbyii, deornatum; Pecten subelongatus; Pinna flexicostata, flabelliformis, membranacea; Pteronites angustatus, persulcatus; Posidonia Becheri; Streblopteria pulchella; Myalina Verneulii; Lithodomus dactyloides; Area cancellata; Bysso-arca costellata; Nucula gibbosa; Leda attenuata; Solemya primaeva; Leptodomus costellatus; Schizodus axiniformis, carbonarius, deltoides; Conocardium elongatum; Edmondia sulcata, unioniformis, arcuata ; Cardiomorpha oblonga, striata; Sanguinolites sulcatus, variabilis, iridoines; Conularia quadrisulcata ; Dentalium dentaloideum, priscum ; Capulus trilobus ; Pleurotomaria atomaria, sulcatula, decipiens, angulata, helicinoides; Euomphalus carbonarius, acutus, catillus, Dionysii; Macrocheilus acutus, Michotianus, limnaeformis; Naticopsis plicistria; Loxonema rugifera, sulculosa, elongata; Platyschisma helicoides; Bellerophon Urii, decussatus, striatus, hiulcus, apertus; Nautilus ingens, globatus, perplanatus, sulcatus, subsulcatus, costata-coranatus; Goniatites sphaericus; Actinoceras giganteum; Orthoceras sulcatum, Gesneri, inequiseptum, attenuatum, fusiforme, cornu-vaccinum, &c.

The Lower or Carbonaceous group, from the base of the Dun Limestone to the top of the Tuedian formation, has a thickness of about 900 feet, and is especially marked by the number, thickness, and quality of its coal seams. In this we have in descending order the following eight seams of workable coal, viz., the Fawcet or Falcet Coal, about 40 feet below the Dun Limestone, is from 18 inches to 3 feet 4 inches thick; the Scremerston Main Coal is from 2 feet to 4 feet; the Stoney Coal from 1 foot to 3 feet 6 inches, but of poor quality; the Main or Cancer Coal from 2 feet to 7 feet; the Three-quarter Coal, of inferior quality, from 2 feet to 4 feet; the Cooper or Cowper Eye Coal, one of the best for domestic use, from 17 inches to 3 feet; and the Wester Coal from 3 feet to 4 feet 6 inches in thickness. There are a few limestones in this division, but they are thin and generally impure, and their aggregate thickness is only about 20 feet. Some of the marine organisms of the calcareous group appear here, but in fewer numbers. In some shale beds remains of ganoid fish are abundant, accompanied by ', Anthrocomya, Aviculo-pecten, ', organisms generally associated with coal seams. This group is intermediate in its characters between the calcareous group of the Mountain Limestone and the Coal Measures; and taking the mass, it is more allied to