546 



J. E. BLAKE ON THE UPPEK 



sion, contain Amm. cymodoce, Natica hernispJioerica, Pteroceras oceani, 

 P. Pontic Mytilus jurensis, Ceromya excentrica, Thracia suprajurensis, 

 and Pinnigena iSaussurei, and are therefore very fair represen- 

 tatives of Pterocerian beds, especially when compared with those at 

 Havre. Neither these beds nor the overlying Yirgnlian marls could 

 be specially examined. 



The so-called Portland beds, however, of the He d'Oleron demand 

 particular attention. As in the Charente department, the upper 

 part is gypseous ; but M. Manes does not on that account call them 

 Purbeck, but classes all with the Portland. The beds are well dis- 

 played along the cliffs and shore of the island on either side of the 

 harbour of St. Denis. The lowest beds seen are (1) massive blue 

 calc grits, which stand out as reefs at low tide on the north of the 

 harbour, and are broken up and stacked on the roads. These contain 

 Ammonites Gravesianus and Trigonia cf. concentrica. They are suc- 

 ceeded by many other beds, forming scars, which are better seen on 

 the south of the harbour, though the succession may not be perfect. 

 The lowest beds seen here are (2) marly limestones and grits, of 

 unknown thickness, more than 4 feet ; next is (3) blue sandy marl, 

 3 feet ; (4) hard blue sandy beds, with circular fucoid markings, 

 with Mytilus Morrisii, Trigonia concentrica ?, Cardium morinicum, 

 and Exogyra nana, 2 feet ; (5) earthy marls, 1 foot ; (6) solid cal- 

 careous block, with Cyprina Brongniarti (broad var.), Lucina port- 

 landica^, Pecten suprajurensis, P. jarnacensis, Cardium dissimile, and 

 Astarte rugosa ?, 1 foot ; (7) alternations of limestones with luma- 

 chelles of Exogyra nana and earthy beds with Cardium Morriseum. 

 6 feet; (8) thin-bedded limestones, with shale and clay, 10 feet. 

 In the cliffs on the north side, separated from the low-water rocks 

 by masses of blown sand, are beds which must succeed the above, 

 but perhaps not immediately. These are (9) alternations of thin- 

 bedded limestones and black sandy marls, with gypsum, possibly the 

 continuation of (8), 12 feet ; (10) black and white sandy clays, no 

 fossils, 20 feet; (11) thin-bedded and laminated clays, 3| feet; 

 (12) black laminated clay and sandy limestones, 8 feet ; (13) purple 

 lithographic suboolitic limestones in thin beds, the uppermost when 

 weathered becoming a vacuolar oolite, and containing masses of 

 shell-fragments, all undistinguishable, unless one is a flattened 

 Cardium dissimih ?, 2 feet. Above this are still some white chalky 

 fragments ; but no more is seen. Here, again, therefore the same 

 argument holds as for the neighbourhood of Jarnac. The fossili- 

 ferous beds cannot be lower than the zone of Cyprina Brongniarti \ 

 and the higher beds must in all probability represent true Portland 

 rocks. The occurrence of Cardium dissimile is especially note- 

 worthy. It is found near the top of the series ; and in no other 

 locality does it occur lower than the true Portland. If the rocks 

 which contain it be of such an age, we must place the overlying 

 gypseous beds in the same category, unless we choose to call 

 them Purbeck. This we should not be justified in doing un- 

 less we had the whole of the Portland limestone here, which is 

 improbable. 



