230 Reviews — Dr. Roice on the White Chalk of Yorkshire. 



absence of some of the commonest zonal fossils, together with the 

 unreliability of others which do exist, which has rendered the task 

 of zoning this Chalk so difiScult, but, withal, so fascinating." That 

 is how the scanty ill-preserved fauna of the Yorkshire Chalk appeals 

 to one who has the art to read its lesson ! 



Now, the meaning underlying this and other similar sentences 

 evidently is that Dr. Rowe, having been able to define the range of 

 most of the Chalk fossils in the cliflf-sections of the South of England 

 within fixed limits, and having found them persistent within these 

 limits in that region, had begun to have faith in these zonal 

 boundaries as representing the full life-history of the species. But 

 his journey northward has impressed upon him that the range of 

 many of his zonal species is not everywhere the same. It is true 

 that he has still managed skilfully to extract sufficient evidence to 

 re-establish Barrois' system of correlation on a firmer basis, and to 

 prove, what was indeed already acknowledged, that the general 

 zonal succession in Yorkshire corresponds to that in the South of 

 England. In studying the range of the individual species, however, 

 and their grouping, he finds that some cherished guides have 

 wandered far from the path of zonal rectitude. Thus we read — 

 " The vertical range of certain fossils, usually restricted in their 

 distribution, is so vast that their very persistence is bewildering. 

 As instances of this contention we may quote a range of 800 feet 

 for Actinocamax granulatus, and 650 feet for Actinocamax verus ; 

 while Cardiaster annnchytis has been traced for 640 feet, and 

 Infulaster rostratus for nearly 700 feet." 



"That Actinocamax verus should be found in the quadratus-chalk ; 

 that Actinocamax granidatus should be found some 350 feet up in 

 the same zone ; that Ivfnlaster rostratus should range from the 

 zoriQ oi Micraster cor-testudinarium to that of ^ci/nocamaa; quadratus; 

 and that Cardiaster ananchytis should extend from the Micraster 

 cor-anguinum-zone to the same horizon, are facts sufficiently unusual 

 to warrant special comment." 



Therefore, although Dr. Rowe and Mr. Sherborn have been able 

 to prove the presence in the Flamborough cliffs of all the zones 

 from that of Rhijnchonella Cuvieri to that of Actinocamax quadratus, 

 inclusive, it is acknowledged that for some of these zones the guide- 

 fossils on which they had been accustomed to rely are inadequate 

 in this district for the identification of the divisions. 



To meet this difficulty Dr. Rowe suggests, though with evident 

 reluctance (p. 219), that in certain cases the name of some other 

 fossil, locally abundant, should be associated with the established 

 name-fossil as its *' local equivalent." We commend the wisdom 

 of this course, for however much it may be desirable to adhere to 

 established zonal nomenclature for purposes of wide-reaching cor- 

 relation, it is unnecessarily perplexing to the student and irritating 

 to the stratigrapher to find that a particular zone is marked by the 

 absence of its name-fossil ! 



Hence the choice of the characteristic Inoceramus lingua as the 

 local guide for the zone of Actinocamax quadratus, since the last- 



