A Freshwater Bed at tlie Base of the L. Carboniferous. 293 



Aviculopecten dissimilis Fleiu. Myalina pemlata de Kon. 

 Lithodomus carbonarkis Hind. Pseudamusiimi ellipticum (Phill.). 

 Myalina verneuilli M'Coy. 



In addition to these a few examples of other forms occur : — 



A large crushed cup coral, of. Zaphrentis enniskilleni Ed. and II. 



Lingula squamiformis Phill. 



Orbiculoidea nitida Phill. 



Fenestella sp. 



Comdaria quadricarinata Sby. 



Euomphalus sp. 



Psephodus cf. fnagnus Ag., and also a few plant remains referable 

 to Pteridorachis. 



This assemblage of forms, though undoubtedly of Lower 

 Carboniferous age, cannot be assigned to any definite horizon in the 

 north of England succession, bat as the bed underlies the Cyrtina 

 carbonaria sub-zone which forms the floor of the quarry, it cannot 

 well be newer than the horizon of the gastropod beds of Westmorland 

 or Si of the Bristol district, and may be of even earlier date. It 

 will be noted that none of these species occurs in the Michelinia 

 zone, which represents the lowest horizon met with in the district. 



The only locality in the North-West Province where the writer 

 has noted lamellibranchs at a low horizon is at Pinksey Gill, Eaven^ 

 stonedale^ below the Shap conglomerate. Here we find casts of 

 Aviculopecten, Lithodomus lingualia and Myalina, associated with 

 species of Lingida, Orbicidoidea, Psephodus and Pteridorachis. 

 The species of the lamellibranchs here, however, are different and 

 on account of their occurrence below the Shap Conglomerate and 

 for other reasons, it is probable that the Pinksey beds are of older 

 date than the Lamellibranch bed at Horton. 



From this description it is evident that the section formerly 

 exposed at Horton is of considerable interest, as it carries back the 

 earliest known occurrence of Viviparus to Lower Carboniferous 

 times at least and possibly even to the Devonian period. 



EXPLANATION OF PLATE XIII. 



Fossils from tlie base of the Carboniferous Limestone, Horton-in-Ribblesdale, 



Yorkshire. 

 Figs. 1-3 from the Viviparus Shale. 

 Fi^s. 4-7 from the Lamellibranch Limestone. 



FIG 



1. 



Viviparus carbonarius sp. no v. 



Viviparus carbonarius. Group of crushed specimens, slightly enlarged. 



Carbonicola angulaia (de Ryckholt). 



Myalina peralata de Kon. 



Myalina verneuilli (M'Coy.). 



AviculojKCten dissimilis Flemmg. 



Pseudaniusium ellipticvm (Phill.). 



^ Q.J.G.S., vol. Ixviii, 1912, p. 496. 



