312 Reviews — Dr. A. W. Rowe— Zones of the White Chalk. 



' Dr. Eowe commences with an excellent description of the cliff- 

 section from White Nothe to Bats Head, which comprises all the 

 zones of the Middle and Upper Chalk from the zone of Bhynchonelia 

 duvieri to that of Actinocamax quadratus. He points out that the 

 layers of yellowish green-coated nodules which had been called 

 'Chalk Rock' really occur in the upper part of the Terehratulina 

 zone, and in no way represent the Chalk Eock. To my own know- 

 ledge it is just the same in the Isle of Wight ; in both areas the 

 equivalent of the Chalk Rock is to be found in the lower part of 

 the zone of Holaster planus, which consists of nodular chalk 

 without any beds of hard limestone. Each zone in the White 

 Nothe section is defined by the range of its characteristic fossils, 

 and of the Act. quadratus zone no less a thickness than 320 feet 

 comes in without any sign of the still higher zone of Belemnitella 

 mucronata, although that is found inland. 



The zonal details of all the other accessible cliffs are treated in the 

 same way, i.e.-, those of Durdle Cove, Man of War Cove, Lulworth, 

 Mupe Bay, Arish Mell, and Worbarrow Bay ; and though in some 

 places the Chalk is so crushed that measurements are of small value, 

 the determination of the zones which enter into the composition of 

 these cliffs carries our knowledge much beyond that of any previous 

 memoir. Finally, the cliffs which extend from Ballard Point to 

 Studland Bay are described as fully as the difficulties of access will 

 permit, and the limits of the zones of Marsnpites, Act. quadratus, and 

 Bel. mucronata in them are for the first time correctly indicated. 



Part III of these studies, being a description of the Chalk of the 

 Devonshire cliffs, was published in May of this year, and is in some 

 respects the most interesting, as it is certainly the most fully and 

 beautifully illustrated of the series, for it includes twelve plates 

 showing portions of the cliffs between Lyme Regis and Branscombe, 

 and each is made illustrative of the zonal geology by means of 

 a key-slip. 



The general stratigraphy of the Devon Chalk has been known 

 since the publication of Professor Barrois' " Recherches " in 1876, 

 for he was the first to ascertain that the greater part of the Lower 

 Chalk is absent, and that the beds which include the Beer Stone 

 belong to the Turonian or Middle Chalk. More detailed and accurate 

 knowledge of the structure of these cliffs has been in my possession 

 for many years, but being destined for a Geological Survey memoir 

 its publication has been long delayed. Meantime Dr. Rowe has 

 visited the coast, and has explored the beds in some places more 

 minutely than I was able to do, the result being an excellent guide 

 to the Chalk of Devonshire. 



Beginning with the Pinhay cliffs near Lyme Regis, he shows 

 that they exhibit good sections of the zones of Bhynch. Cuvieri, 

 Ter. gracilis, Hoi. planus, and Micr. cortestudinarium, and his careful 

 collecting of fossils has enabled him to delimit the zones in this 

 section more accurately than any previous observer. The same 

 succession is found again at Beer and at Beer Head, and I agree with 

 him that the summit of the zone of Micraster cortestudinarium is not 



