Correspondence— F. R. C. Reed. 527 



of the European fauna in the form of a little book, as it was not 

 so easy for the student to obtain access to the original paper in the 

 Eoyal Irish Academy's Proceedings. The illustrations add greatly 

 to the interest of the volume, but they might well have been more 

 numerous. We are sure it is a book which will have many readers 

 and some few critics. We have already made some criticisms on 

 the original paper,^ and will now only commend it to our readeis 

 in its present form as a most attractive little volume on a most 

 fascinating subject by a very able and clever Naturalist. 



coI^I^Es:po^:s^ID:BI^rc:E!. 



THE LIMESTONE KNOLLS OF THE CRAVEN DISTRICT. 



SiK, — In a recent suggestive paper on the Limestone Knolls of 

 the Craven District (Q.J. G. S., vol. Iv, 1899, pp. 327-358), 

 Mr. Marr's criticisms of my views on the Keisley Limestone appear 

 to demand some reply, as nnfortunately I was not present when his 

 jiaper was read. I do not intend to examine the plausibility of 

 Mr. Marr's views of the origin of the Craven knolls, with which 

 I have only a slight acquaintance in the field, though, as I have paid 

 some attention to their fossils, I may remark in passing that he does 

 not bring forwai'd the least paleeontological evidence in support of 

 his conclusions. It is the neglect or lack of appreciation of the 

 ))ala3ontological evidence furnished by the Keisley Limestone by 

 wliich he escapes tlie difficulties in which he would otherwise be 

 there involved. For it is not here a case, as Mr. Marr appears to 

 think (op. cit, p. 356), of the relative abundance of fossils, but of 

 an assemblage of fossils with a facies entirely distinct from that of 

 the neighbouring strata. When Mr. Marr can prove that the fauna 

 of the thin white limestone which apparently represents strati- 

 graphically the Keisley Limestone is identical with the fauna of the 

 latter, his conclusions will rest on a firmer basis. Moreover, in 

 order to demonstrate that the theory of discontinuous distribution 

 is untenable, Mr. Marr must be able to prove the genei-al 

 distribution of the peculiar Keisley Limestone fauna over the 

 intervening areas ; otherwise he must acknowledge that some 

 special local biological or physical conditions contributed to the 

 congregation of this fauna in isolated colonies. Modern instances 

 of discontinuous distribution with stations of limited superficial 

 area admittedly offer problems hard to solve, but we cannot shut 

 our eyes to their existence ; and there is no a priori reason why 

 similar instances should not be discovered in the records of the 

 past, though naturally the difficulties of fully explaining them would 

 be increased in dealing with extinct species. 



It is needless here to recapitulate my reasons for drawing my 

 conclusions as to the nature of the Keisley Limestone fauna; some 

 of the less important ones ai'e quoted and discussed by Mr. Marr, 

 but the more important detailed palgeontological evidence which 

 he omits can be studied in my papers (Q.J.G.S., vol. Hi, 1896, 

 1 See Geol. Mag., 1897, pp. 420 and 468. 



