The Carboniferous Limestone of West Cumberland. 19 



like annelids, small gastroiiods, Calcisphcera. 

 Shales contain lamellibranchs, Avicidopecten cf. 

 plano-clathratas McCoy and Modiola sp. 



Seventh Limestone . Productus maximus McCoy, P. cora d'Orb. mut. So, 

 P. corritgato-hemisphericus Vaughan abundant 

 and characteristic. P. scabriculusMeiTt., Dielasma 

 cf. sacculus (Mart.), Seminula ci.ficoidea Vaughan, 

 Cyrtina sp., Cyathophyllum cf. <f> Vaughan, 

 N ematopTiylhun minus McCoy, Carcinophyllum 

 sp. near Q Vaughan, Caninia cf. patula Mich. 

 Syringopora sp. [a distinct form]. 



Basement Beds . . Plant impressions and casts of Productus. 



General Lithological Description op the Series. 



The series consists of a number of massive to thinly bedded lime- 

 stones interspersed with beds of sandstone, shale, or mudstone (see 

 Tables I and III). 



The limestones are most commonly of standard type, viz. with 

 a standard marine fauna. Their texture ranges from coarse granular 

 crinoidal rocks to very fine-grained or porcellanous " calcite- 

 mndstones 'V which include " chinastone-limestones ". In colour 

 they vary from white through reddish-grey and blue to almost black, 

 beds on the same horizon differing according to the presence or 

 absence of haematite in the vicinity. 



The shales and mudstones range in colour from pale green or grey 

 through reddish-grey to purple and black ; in thickness from 

 paper-thin partings to beds 12 to 14 feet in thickness. The mud- 

 stones associated with the Fourth Limestones are mottled (white, 

 red, and purple), and are either purely argillaceous (weathering to 

 a crumbly clay) or sandy-argillaceous ; they are known in the district 

 and are recorded on the Vertical Sections published by the Geological 

 Survey as mottled shales. The shales in the upper limestones are 

 carbonaceous. Mica is usually present in the sandy shales, but is 

 absent from the mudstones. The sandstones intercalated between 

 the limestones are generally stained red and purple, and, with the 

 exception of one or two coarser bands in the Orebank Sandstone, 

 are mainly fine-grained. Mica is usually present. No limestone 

 exactly like the Bryozoa Bed (Hor. «) of Bristol is present, but 

 rocks somewhat resembling it occur near the base and summit of 

 the Seventh or Bottom Limestone and again near the top of the 

 Fourth Limestone. A rock suggesting the " Seminula Pisolite " of 

 the Avon Section occurs near the summit of the Seventh Limestone. 



Subsequent dolomitization occurs locally in many of the lime- 

 stones ; it is frequently associated with hsematite. Dolomite- 

 mudstoues are common at the base of the series, but no con- 

 temporaneous dolomitization has been observed. A fine-grained 

 calcite-mudstone, about 2 feet thick, weathering white and fracturing 

 conchoidally, like the " chinastones " of the S.W. Province, occurs 

 midway in the Seventh Limestone, whilst other calcite-mudstones, 



^ The terms " calcite-mudstones " and " dolomite-mudstones " are used for 

 rock-types similar to those described by Mr. Dixon {op. cit., pp. 516-17). 



