Vol. 68.] SUCCESSION IN THE NORTH-WEST OF ENGLAND. 467 



imder description. It has never been found in the upper portion of 

 the zone, and with the exception of two rolled specimens collected 

 from the Ashfell Sandstone, no occurrence of this form above the 

 present horizon is known. AiJiyris glahristria also occurs sparingly, 

 together with a fine mutation of CyaiJiopJiyllum multilamellatum . 



Geographical distribution. — This sub-zone is represented 

 in all the districts. It is well exposed in Docker Beck in the Shap 

 District ; at Elliscales in the Furness District ; at Frith Hall and 

 Cat Crag in the Grange District; at Meathop in the Arnside 

 District ; and above Brigsteer in the Kendal District. In the 

 Ravenstonedale District it cannot be clearly separated from the 

 upper portion of the zone. It is represented by unfossiliferous 

 sandstones in the Pennine District. 



(d) The Chonetes-carinata Sub-zone. 



The upper portion of the Michelinia Zone is especially charac- 

 terized by the occurrence of large specimens of Clionetes carinata 

 (nobis MS.), a species confined to this sub-zone in the J^orth- 

 Western Province.^ It is associated with Michelinia grandis and 

 M. tenuisepta, together with Caninia cylindrica and Cijatliopliyllum 

 nudtilamellatum. The upper limit is defined by a band which 

 is marked by the abundance of Clisiopliyllum multiseptatum and 

 Zaplirentis ennisldlleni. The beds are best developed in the dis- 

 tricts bordering Morecambe Bay, and are especially Avell exposed 

 along the shore to the west of Arnside ; the latter exposure 

 may, therefore, be taken as the fullest development of this sub- 

 zone. Complete sections showing the relation of the two sub-zones 

 one to the other occur at Frith Hall on the Leven Estuary ; above 

 Brigsteer in the Kendal District ; and at Elliscales in the Furness 

 District. 



Lithology. — The rock is essentially a grey calcareous mudstone, 

 enclosing harder layers of cement-stone. Some of the beds are 

 shaly, especially towards the summit. In the Kavenstonedale 

 District the sub-zone is represented by a small thickness of red 

 and grey calcareous shales ; but here this sub-zone is not so 

 distinctly differentiated from the underlying beds as in the Western 

 Districts. At Docker Beck, in the Shap District, it is apparently 

 represented by the lower unfossiliferous portion of the Ortou 

 Sandstone. 



Fauna. — The fauna is, on the whole, the richest, both in species 

 And individuals, of any horizon in the North- Western Province. It 

 aIso contains some of the largest forms of corals and brachiopods. 

 In addition to the species mentioned above, Zaplirentis Iconindci and 



1 Tbis form appears to be identical with Choncies aff. comoidcs of 

 Dr. Vaughan, Q. J. G. S. vol. Ixi (1905) p. 295. 



2 51 2 



