Revieivs — Cretaceous Rocks of Britain. 177 



historical interest and valuable as defining the position taken by 

 the authors in dealing with their subject. 



Defining next the ' Lower ' Chalk, the authors point out that this 

 is divided into two zones, that of Ammonites varians and that of 

 Solaster subglohosns. They also include in the latter the Actinocamax 

 planus marls, which " do not constitute a zone, and have no distinct 

 zonal fauna," and they follow with a description and lists of the fossils 

 which are eharacteristic of the beds. 



Chapter iii deals with the ' Lower ' Chalk of the Kentish coast,, 

 the classical section of which is to be found between Folkestone and 

 Dover, and was the subject of the especial study of Mr. Hilton Price, 

 who divided the two zones up into nine beds. Some slight modi-, 

 fications of Mr. Price's work is suggested ; beds 3 and 4 are 

 united, but the rest seem to have stood the test of recent research. 

 Leaving the coast, a general description of these beds in the inland 

 parts of Kent and Surrey is given, and Hampshire and Sussex are 

 similarly treated, attention being called to the section between 

 Beachy Head and Eastbourne, the beds in which are, however, too 

 much disturbed to allow of a definite section being given. 



Chapter vii introduces us to the Isle of Wight, and includes 

 several important observations both as to the sections and the fossils, 

 made since the second edition by Strahan and Eeid of the memoir 

 on that island, which was published in 1889. It is pointed out 

 that the use of the words " Chloritic Marl " is continued because 

 it is convenient and has been so long in use, but at the same time 

 the green grains are not chlorite and the matrix is not a marl. 



Chapters viii-xix deal in similar manner with the counties of 

 Dorset, Somerset, Devon, Wilts, Berks, Oxford, Bucks, Beds, Herts, 

 Cambridge, Suffolk, Norfolk, Lincolnshire, and Yorkshire ; and 

 Chapters xx and xxi provide a useful sketch of the beds of similar 

 age in the north-east and north-west of France. 



The Middle Chalk (the lowest beds of the White Chalk) is 

 defined as consisting of the zones of Ehynchonella Cuvieri and of 

 Terebratidina. This latter zone has long been known as the zone 

 of TerebratuUna gracilis, but Dr. Kitchin is quoted as pointing out 

 that the true gracilis is confined to the higher beds of the White 

 Chalk, and that the form so common in the TerebratuUna zone seems 

 to be that called T. gracilis, var. lata, of Etheridge. The ' Middle ' 

 Chalk is then described in similar detail to the ' Lower ' Chalk, the 

 authors proceeding county by county and tabulating a vast amount 

 of valuable material in the several chapters. We see here for the 

 first time the influence of the careful zoological work done in recent 

 years by Dr. Eowe, of Margate, whose collecting has more definitely 

 proved the boundaries of the several zones of the White Chalk. 

 The ' Middle ' Chalk portion of the memoir closes with a chapter 

 on the French equivalents, allowing a comparison to be made at 

 once useful and convenient. 



Chapters xxii, xxiii and xlii, xliii are written by Mr*. Hill, and 

 treat of the microscopical structure of the rocks described in the 

 memoir. Mr. Hill describes the macroscopic aspect of the rocks and 



PECADE T. VOL. I. NO. IV. 12 



