426 DK. HANS SALFELD ON CERTAIN [Oct. I913, 



as also the Gr.avesia and Virgatites Beds of the Lower Portlandian, 

 cannot be recognized here, because the section is, to a great 

 extent, obscured by talus. 



The clays below the Portland Sands here likewise yield Peri- 

 sphinctes pallasianus throughout. 



The section at Red Lane, Abbotsbury, described by Blake & 

 Hudleston l (given by them in inverted order of succession) shows 

 in Bed 2 of Blake a dark-brown, richly-ferruginous, soft oolite, 

 containing in abundance Waldheimia dorsetensis Walk., Rasenia 

 thermarum Oppel sp., B. uralensis d'Orb. sp., and other species. 

 These ' Corallian Beds ' of Blake are, therefore, the exact equi- 

 valents of the Lower Kimmeridge Clay of Weymouth, the zone of 

 llasenia cymodoce, a fact already recognized by Prof. H. Douville. 



The exposures near Swindon prove that the Kimmeridge Clay 

 facies, as shown in the clay-pit at Telford Road, extends down 

 as far as the zone of Perisphinctes d.ecipiens and Cardioceros 

 serratum. Below this follow sandstones of the ' Corallian.' Clays 

 with Pictonice are exposed at the base of Buzzard's Clay-pit in 

 Swindon. The leathery shales at the top of the Lower Clay -pit 

 contain Aulacostephanus pseudomutabilis, A. eudoxus, etc. Since 

 the succeeding clays and marls yield Virgatites, the dividing-line 

 between Kimmeridgian and Portlandian must here be placed 

 immediately above the leathery shales. The Oravesia Beds are 

 here either entirely wanting, or are condensed to a minimum. 



It is known that Perisphinctes pectinatus occurs in the Portland 

 Sands below the Swindon Clay. The Swindon Clay itself has 

 yielded no ammonite. On the other hand, the 'Lydite Pebble- 

 Bed,' immediately overlying the Swindon Clay, contains a new 

 ammonite of contemporaneous age — a Perisphinctes related to 

 P. ulmensis Oppel sp., P. denseplicatus Waagen, and P. j>ost- 

 idmensis Blaschke — in addition to very numerous, rolled, phos- 

 phoritized and silicified fossils derived from lower horizons, parti- 

 cularly from the zone of Perisphinctes pallasianus. Immediately 

 above, in the base of the calcareous sandstone, Perisphinctes gorei 

 sp. nov. is abundant. The main mass of the calcareous sand- 

 stone yields Perisphinctes pseudogigas Blake sp. as the charac- 

 teristic species. The overlying Swindon Sands may be regarded 

 as equivalent to the zone of Perisphinctes giganteus, although it 

 has not been possible to prove the occurrence of ammonites in 

 them. 



It is important to note that, in the Swindon neighbourhood, the 

 sandy facies persists longer than at Portland and in Purbeck. The 

 boundary which is there drawn between the Portland Sands and 

 the Portland Oolite would fall at Swindon in the calcareous sand- 

 stone, above the zone yielding Perisphinctes gorei. 



At Westbury the top of the Ironstone yields B.ingsteadia> ; above 



1 J. F. Blake & W. H. Hudleston, ' On the Corallian Rocks of England ' 

 <Q. J. G. S. vol. xxxiii (1877) p. 273. 



