Reviews — Prof. Prestwich on the Past and Future. 375 



Up ware and Potton, viz. the light yellow varying to dark brown, 

 almost to the black type, much worn before they reach the mill, 1 and 

 perforated by lithophagous mollusca and annelids. They contain (at 

 Potton) about 48-51 per cent, of phosphate of lime. 2 



In conclusion, I may remark on the wide distribution of these 

 Neocomian " coprolites." They occur at Farringdon, Brickhill, 

 Eushmoor, Potton, Upware, and I have lately found them in the 

 Upper Neocomian Sands of Lincolnshire. In all these places they 

 are of the same type, much worn and drilled, and abounding with 

 Ammonites biplex and other Kimmeridge-clay forms. This fact of 

 the Kimmeridge-clay origin of so many of these " coprolites " is of 

 importance in considering the origin of the phosphatic matter ; for 

 since we do not find the fossils in this phosphatised condition 

 abundantly in the Kimmeridge-clay, while they are invariably so 

 over a wide extent of country as derivative fossils in the Neocomian, 

 we may infer that the phosphate was obtained in the latter period ; 

 in other words, as suggested by Mr. Walker, 3 that the coprolites are 

 nodules derived from the Kimmeridge-clay, which have been 

 " soaked " with phosphates obtained by the decomposition of animal 

 and vegetable matter in a shallow sea, 4 with, perhaps, some replace- 

 ment of the phosphate of lime for carbonate of lime. 



I may observe also that at Potton fossils in this eroded condition 

 occur of the Portland and Wealden ages — notably the Endogenites 

 erosus of the Weald — indicating, as I believe, the former extension of 

 these deposits near, if not quite up, to this locality. 5 Further north, 

 at Upware, Endogenites erosa has not, to my knowledge, been 

 found, and the Dinosaurian remains are much less frequent; so 

 that the northern limit of the Wealden may reasonably be fixed at 

 some place not far from Potton. 6 



EEYIE W S. 



I. — The Past and Future of Geology. An Inaugural Lecture given 

 by Joseph Prestwich, M.A., F.E.S., F.G.S., etc., Professor of 

 Geology in the University of Oxford, January 29, 1875. pp. 48, 

 with four illustrations. (London : Macmillans.) 



ME. PEESTWICH, after paying a just compliment to Oxford 

 by noting how much the infancy of modern Geological Science 

 was indebted to the labours and discoveries of Kidd and Buckland, 



1 The eroded appearance of the Cambridge coprolites has frequently, and to a great 

 extent incorrectly, been referred to the trituration produced by washing in the mills. 



2 Vide analysis by Dr. Voelcker, Geol. Mag. 1866, Vol. III. p. 154. 



3 Ann. Nat. Hist. Nov. 1866. 



4 This theory has no reference to the nodules of the Gault and Cambridge Green- 

 sand, which are far too pure for sucb an origin. 



5 Professor Morris has already (Geol. Mag. Vol. IV. p. 459) from similar evidence 

 stated bis conviction that the Wealden beds were present over the neighbourhood 

 of Aylesbury. 



6 M. J. Harris Hall, of St. John's College, informs me that he found coprolites 

 scattered over this hill at Brickhill about two years ago. The result of his inquiry 

 into the Potton and Upware deposits (Sedgwick Prize Essay) will be published 

 very soon. 



