174 Reviews — Professor Charles Barrois — 



with varying degrees of accuracy the limits of every zone. The 

 scenery of this boklly sculptured coast is controlled by the influence 

 of the great Isle of Purbeck fault. Inland the beds are horizontal 

 (Wool), and the clialk is so soft that it may be crushed between the 

 finger and thumb ; on the coast the beds are folded, broken along the 

 Purbeck fault, and the chalk itself so compacted that it needs to be 

 cut with the chisel. All large fossils are broken, the fragments of 

 the belemnites are often considerably displaced, and the flints 

 shattered into pieces and often drawn out into long dusty lines. 

 Finally, the thickness of the beds themselves is modified, the cuvieri- 

 and Terebratulina-zo'ae^, normally about 134 feet thick where horizontal 

 inland, are reduced to 70 feet on the coast (Durdle). 



One of the most remarkable features of this coast is seen at Durdle 

 Cove among slide-planes, where the beds have been pushed northward 

 over one another, ground up into a paste at the junction and 

 re -cemented, thus exposing the Terelratidiiia-zone above and the 

 plriniis-zone below, and the planus-zone above and the Micraster cor- 

 testudinarium-zone below by the cutting back of the cliff by the sea. 

 Notwithstanding the complexity of such inverted succession, the 

 determination of the exposed masses by means of Micraster was so 

 definite — the determination being impossible to obtain in any other 

 way — that it s])eaks highly for the author's method. 



Much new information has been given about these complicated 

 sections and poor faunas of Dorset, especially as regards the higher 

 zones. The Marsupites- zone yields a fairly rich fauna, and, what is 

 more important, a fauna which closely agrees with that from the same 

 zone on the coast of Kent and Sussex. As regards the belemnites of 

 the higher beds, we note that Actinocamax quadratus is limited to 

 a narrow band about the middle of the zone, and A. gramdatiis to the 

 extreme base of the same zone, whilst Belemnitella vimcronata and 

 B. lanceolata are found in profusion from base to top of their zone. 



Devon. 



If the chalk exposures of Dorset afford views of greater variety and 

 physical features more complicated and remarkable, those of Devon 

 are of special interest on account of the accessibility of the cliffs and 

 the unaltered state of the Chalk. JS^o section on the English coast 

 gives so much detail or tells the story of zonal succession in so con- 

 vincing or so graphic a manner. It affords a scope for the study of 

 the Echinoidea which would alone render it famous. 



Giving a limited exposure from the cuvieri- to the M. cor- 

 testudinarium-zone, it differs from all other sections by the varying 

 zonal measurements. The Terehratulina-zone^ for instance, A-aries 

 from 70 to 156 feet in a comparatively short distance, and the 

 cuvieri-zone from to 80 feet. Many facts point to littoral conditions, 

 showing that in Devon we get nearer to the western shore of the 

 Cretaceous sea, as we do in the western part of the Paris Basin. 

 Throughout the M'hole coast there are few lithological characters on 

 which we can rely for more than a quarter of a mile, and this 

 uncertainty applies with equal truth to measurements and to the 

 distribution and variety of the fauna. 



