Vol. 68.] SUCCESSION IN THE NORTH-WEST OF ENGLAND. 541 



The shales and basement-beds are apparently unfossiliferous, but 

 specimens of Nematophyllum minus altered into saccharoidal lime- 

 stone have been collected from the overlying limestone. This 

 indicates that the base of the Lower Scar Limestone in Teesdale 

 lies as in the case of the Pennine escarpment, in the N.-minus 

 Sub-zone. 



The Lower Dihiinophyllum Sub-zone is found overlying 

 the Whin Sill on Widdybank Moss, but is also much metamor- 

 phosed. Below High Force no further exposure of these lower 

 beds is seen, the Yoredale Beds being here brought in by the 

 Burtreeford Eault, so that they occupy both sides of the valley 

 as far as Middleton-in-Teesdale. 



The Upper Dihuyiopliyllum Sub-zone, composed of the 

 Lower Yoredale limestones up to the Great Limestone, contains a 

 fauna similar to that already described. Some of the intercalated 

 shales are rich in fossils. A good exposure of a fossiliferous shale 

 occurs above Holm-Road Bridge in Huddeshope Burn. This appears 

 to be near the horizon of the Pour-Fathom Limestone, and is rich 

 in the remains of brachiopoda and bryozoa. 



Fauna. 



Cliothyris royssi (L'Eveille). 

 Frod'uctus cf. edelburgensis Phill, 

 Froductus longisplnus Sby. 

 Produchts punctatus Mart. ^ 

 EMpidomella michelini (L'Eveille). 

 Spirifer hi?,ulcatu8 Sby. 



Loxonema sp. 

 Murchisonia sp. 



Orthoceras sp. 

 Fhillipsia farnensis Tate. 



Aulophyllum cf. 'pachyendothecum 

 Thomson. 



Cystodictya sp. 



Fenestella memhranacea (Pbill.). 

 Fenestella nodtUosa (Pbill.). 

 Fenestella plebeia M'Coy. 

 Goniocladia ceUulifera Eth. jun. 

 F'bmatopora sp. 

 Folypora sp. 

 Ehahdomeson sp. 



Orbiculoidea nitida (Phill.). 



The higher Yoredale Beds, from the Scar Limestone upwards, are 

 best studied in the sections and quarries exposed in the Huddeshope 

 -and Snaisgill valleys north of Middleton, and along the road 

 between Middleton and Brough. The beds are throughout charac- 

 terized by the abundance of Dlhunophyllmn muirheadi. In the 

 Oreat Limestone, in addition to Productus giganteus, Pr. latissimus, 

 and other characteristic Yoredale forms, we meet with a large 

 •€olumnar form of Lonsdcdia which appears to differ specifically 

 from L. Jloriformis of the Lonsdalia Beds at the base of the 

 zone. Many of the shales are rich in lamellibranchs, and casts 

 of brachiopods occur frequently in the sandstone layers. One 

 such band crowded with Sjpirifer cf. hisulcatus forms the highest 

 fossiliferous horizon of the Yoredale Series in Teesdale, and the 

 same band appears to extend into the upper part of Weardale.^ 



^ Casts of this species show, along tbe inner margin of the hinge-line of the 

 pedicle-valve, a row of pits wbieb must represent, either casts of spine-bases, or 

 ^ row of granules that forms an articulating surface between tbe two valves. 



