-510 TEOE. E. J. GA.EWOOD OJf THE LOWER CAEBO^^^EROFS [DoC, I912, 



It is true that no specimens of Zaphrentis I'oniacki have been found 

 in the Ronaldsway Beds, although I have speciall}' sought for them ; 

 it is difficult, however, to ignore the weight of evidence derived 

 from the above association. Dr. AVheelton Hind has expressed the 

 opinion that the Konaldsway Beds of the Isle of Man belong to the 

 Dibunopliyllum Zone,^ and the same author ]ias expressed to me his 

 strong conviction that the Arnside Beds are also of Dihunophyllum 

 age. It is possible that this view was founded, in part, at all 

 events,, '<n the presence of Zaphrentis enuiskilleni in both sections. 

 In the isle of Man, however, that form is not confined to these 

 lower beds, but passes up into beds which are (at all events) high 

 in S if not actually of Dihunophyllum age. All the beds of the 

 succession are dark argillaceous and bituminous limestones, and 

 it seems highly probable that we have here an example of the 

 dependence of faunal development on lithological character, and 

 that Z. ennislcelhni continued to flourish in the Isle of Man area 

 through a considerable period of time — as long as the conditions 

 remained suitable. At Arnside, on the other hand, the typical 

 corals of the argillaceous Chonetes-carlnata Beds disappeared with 

 the subsidence which introduced clearer water conditions and white 

 limestone deposits. Where Zaphrentis enniskiUeni occurs in the 

 Upper Dihunophyllum Zone in other areas, it is again associated 

 with argillaceous limestones. 



The Prodiictus-corrugato-hemisphericus Zone is charac- 

 terized by the absence of the sandstone episode of the type- 

 districts, the beds being fairly fossiliferous throughout. The lower 

 portion is a dark crinoidal limestone, fossiliferous at the base, but 

 becoming compact and rather barren towards the summit. The 

 iip])er portion is a pure pale-grey limestone, compact near the base 

 but platy above. 



The Gastropod Beds form a semicircular outcrop round the 

 northern base of Arnside Knott, and overlie the Mlclielinia Bed of 

 the coast. The upper boundary lies round about the 200-foot 

 contour on the north-eastern flank of the Knott, but there is no 

 hard-and-fast line of division between the two portions of the zone. 

 The beds are seen in the upper part of the cliff near Arnside, behind 

 ^N'ew Barns Farm, in Gubbins Wood and Frith Wood ; and between 

 Blackstone Point and the edge of the salt marsh to the south of 

 Arnside Point, where they are much altered, and roughly cleaved 

 by close-set vertical joints. They are also occasionally exposed 

 in the upper portion of Arnside village, when foundations are being 

 dug for new buildings ; they are fairly fossiliferous, and towards 

 the base contain a band of small SeminuJa ficoidea. The fauna is 

 in some respects similar to that of the underlying Jlichelinia Beds, 

 but it is devoid of Michellnia and Chonetes carinata, and abounds 

 locally in specimens o{ Lithostrotion. The higher and more massive 



1 'The PaliTontological Succession of the Carboniferous Kocks in the South 

 of the Isle of Man ' Proc. Yorks Geol. Soc. n. s. vol. xvi, pt 2 (1907) p. 39. 



