232 Reviews — Di\ Rowe on the White Chalk of Yorkshire. 



difference between the fauna of corresponding horizons in Yorkshire 

 and in Kent. It is true that in the Lower Cretaceous the difference 

 between the two areas is even more conspicuous, but in this case 

 we are dealing with beds of diverse lithological composition, and 

 ■with complex geographical conditions that are sufficient to explain 

 the anomalies. 



What is the meaning of this extraordinary diversity within the 

 same geographical province? We can scarcely believe that climatic 

 variation due to the trifling difference in latitude could make itself 

 directly felt at the bottom of the compai'atively deep Upper Cre- 

 taceous sea. Can it have been due to the influence of cold-water 

 currents creeping down from the north ? Or may we surmise that 

 some of the life-forms themselves in spreading from separate centres 

 of dispersal have exerted a mutually antagonistic effect upon each 

 other, so that they could not pass freely beyond their respective 

 frontiers ? Or is it, after all, only that ever-present mischief-maker, 

 ' the imperfection of the geological record,' that is to blame for our 

 difficulties ? 



We hope that at some future time Dr. Eowe will deal more fully 

 with this fascinating problem, for assuredly he is peculiarly well 

 qualified for the task. And in doing so we shall expect that he 

 will give us that comparison of the Yorkshire fauna with the fauna 

 of the equivalent beds in Germany which is referred to (p. 284), 

 but at present withheld. This comparison is likely to be of singular 

 interest, for apparently some portions of the Yorkshire Chalk have, 

 like portions of the Speeton Clay, closer faunistic affinities with the 

 equivalent rocks of Germany than with those of the South of England. 



In laying stress upon this aspect of Dr. Rowe's results we must 

 not omit to call attention also to the discoveries of the author 

 which go to strengthen the correlation between the northern and 

 southern Chalk. Thus, his recognition of the plentiful occurrence 

 of Uintacriniis in Yorkshire in its customary position at the base of 

 the Marsupites-zone is a notable bond in the correlation and an 

 advance on our previous knowledge. Several other southern fossils 

 not hitherto recorded from Yorkshire have now been identified and 

 are included in the new list. 



The value of the author's method from the stratigraphical point 

 of view is strikingly exemplified by his discovery that the zone of 

 BhjncJionella Cuvieri is absolutely crushed out for a space by the 

 overthrust fault in the Buckton Cliffs. The character of the dis- 

 turbance at this place had been previously recognized, but its effect 

 upon the sequence was unknown until established by the palaeonto- 

 logical evidence. 



Another result given in this paper which the local geologists will 

 be eager to apply in the field is the demonstration of a progressive 

 deepening in the alveolar cavity of Actinocamax graniilatus when 

 this fossil is traced upward through the quadratus-zone. We con- 

 gratulate Dr. Kowe on his acumen in seizing upon practically the 

 only organism of the Yorkshire Chalk which is sufficiently abundant 

 and well-preserved to allow its zonal variation to be worked out. 



