Vol. 68.] SUCCESSIOI!^ IN THE IfOETH-WEST OF ENGLAND. 509 



name for the Arnside form is retained here, so as to prevent 

 any doubt as to which form is intended in this paper. There is, 

 however, a marked difference in size between the Arnside speci- 

 mens and the reef-like masses which occur in the Camarophoria- 

 isorhynclia Sub-zone below ; neither does the latter form show the 

 well-developed epitheca characteristic of the Arnside specimens. 

 M. tenuisepta is also fairly abundant in the Arnside section, and 

 grows to a considerable size. A list of the fauna from this locality 

 has already been given (see p. 468). M'Coy's tj^pe-specimen of 

 Cyathopliylliim midtilamellatum preserved in the Sedgwick Museum 

 was probably obtained from this bed. Specimens of Ohonetes carinata 

 occur abundantly, with the keeled valve lying uppermost. On the 

 shore close to the Crown Hotel, large specimens of Caninia cf. cylin- 

 drica occur, crushed perfectly flat ; and Dr. Sibly informs me that he 

 has met with the same form, similarly flattened, at the same horizon 

 in the Mendip area. West of the bathing-house, the beds crop out 

 at intervals along the foreshore, while a small fault which runs down 

 the bay to the east of ISTew Barns Farm brings in the beds with 

 CJionetes carinata again, north of the farm. At Blackstone Point 

 the junction of the Michelinia Zone with the beds of the overlyinsj; 

 zone is well seen in the old quarry, and in the cliff to the west of 

 the limekiln. Caninia cylindrica occurs here in great plenty. 



The ClisiopJiyllum-multiseptatum Band is well exposed 

 above the limekiln at Blackstone Point, as a bed of dark shale 

 containing abundant specimens of the index-fossil, together with 

 Zaphrentis enniskiUeni and Cyat/iopJiyllam multilameUatum. This. 

 layer is immediately overlain by the earliest Litliostrotion seen in 

 the section, and may conveniently be taken as the dividing-line 

 between the Michelinia Zone and the Froductus-corrugato-liemi- 

 sphericus Zone. 



The occurrence of Zap)7irentis enniskiUeni in beds representing 

 C^ of the Bristol succession deserves some comment. The exact 

 horizon of the beds in which it was first collected in Ireland does 

 not appear to be known, but the species was originally considered 

 to be characteristic of D^. A closely similar, if not identical, form 

 has lately been recorded" from S^ (?) by Mr. James Douglas ^ from 

 County Clare, and is found also, as mentioned above, with variants 

 in the upper portion of the Ashfell Sandstone, below the Cyrtina- 

 carhonaria Sub-zone, and therefore in beds of an age equivalent to 

 S^ of the South- Western Province. In the Isle of Man I have found 

 this species occurring abundantly in the lower beds exposed on the 

 shore at Konaldsway (Derbyhaven), where it is associated with 

 Michelinia grandis, Chonetes carinata, Syringoihyris cuspidata, and 

 the large forms of Schelliuienella crenistria recorded from Arnside. 

 This association is found nowhere in the ISTorth-Western Province 

 outside the Michelinia Zone, and it seems more than probable that 

 the horizon of the Ponaldsway Beds in the Isle of Man lies near 

 the top of C2 and the base of S of the South-Western Province.. 



1 Q. J. G. S. vol. Ixv (1909) p. 554. 



