378 DR. W. HIND AlfD MR. J. A. HOWE ON THE [Aug. I9OI, 



first few feet of the Shales, although they are present in large 

 numbers some 30 feet above the base of the Shales. 



A few species of brachiopoda — Orthis resupinata, Athyris am- 

 higua, Spirifera glabra, Sp. bisulcata, Productus semiretieidatus, 

 Pr. Cora^ Pr. longispinus, Pr. punctatus, Pr. scahriculus, Discina 

 nitida, and a species of Rhynclionella — do certainly pass up from 

 the lower series, and occur, generally rather dwarfed, at one or two 

 horizons in the upper. Of lamellibranchs, Edmondia umoiiiformis, 

 Myalina Flemingii, M. Verneuilii, and a few other species also 

 pass up. The goniatite, Glyphioceras crenistria, said to be common 

 to both series, has never been found by us to pass up. It occurs 

 in lists of Pendleside fossils, but we have never yet seen it in 

 these beds ourselves, and think it very probable that an error of 

 determination has occurred. 



The upper fauna is characterized by a number of peculiar 

 aviculoid and mytiloid forms, referred to Pos-idonomya and Posido- 

 niella, and some species of Aviculopecten -, also by numerous 

 cephalopoda — Glyphioceras reticulatum^ Gl. spirale, Gl. hilingue, 

 Gl. diadema, Gastrioceras carbonaHum, and G. ListeH. 



In the districts mentioned above, the cessation of the lower fauna 

 as a whole, at the limit which we have indicated, is abrupt and 

 final ; and even where pure limestones occasionally appear in the 

 shales, there is no reappearance of the lower limestone-fauna. On 

 the other hand, in the series of limestones, shales, and sandstones 

 of Wensleydale, a recurrence of similar lithological characters is 

 attended by a repetition of the limestone-frequenting fossils. 

 Speaking generally, the fauna of the Lower Scar Limestone and 

 that of the Yoredale Series of Wensleydale is one and the same ; 

 although, as might naturally be expected, certain forms occur in 

 the shales which may be altogether absent from the limestones. 

 This, however, is due to bathymetrical distribution and to the 

 conditions indicated by the nature of the deposit, certain species 

 preferring muddy and others clearer sea-bottoms. 



Moreover, the life-assemblage of the Great Scar Limestone and 

 the true Toredales is identical with that of the massive limestone 

 of the southern type of rocks ; but in individuals and species the 

 latter is much richer than the former. 



At present, in the area of the northern type of Carboniferous rocks, 

 no indication has yet been found of a fauna between the Millstone Grit 

 and the Yoredale Limestones at all equivalent to that in the Upper 

 Limestone-Shales (Pendleside Group) of the southern area. The 

 fauna of the alternating shale and limestone of the northern type 

 has a close affinity with those of the Upper and Lower Limestone 

 Series of Scotland, where the shales and limestones each possess 

 fossils respectively peculiar to one or the other, but certain species 

 are common and give an uniform facies to the whole. The large 

 brachiopoda and corals are often absent from the shales; lamel- 

 libranchiata and small gasteropoda are more common in them. 

 Lingula and Discina, Orthis Michelini and Chonetes Laguessiana 

 seem to have been the chief brachiopods that preferred a muddy 

 environment. 



