730 J. W. JTTDD ON" THE SECONDARY EOCKS OP SCOTLAND. 



coral and many fragments of Inoceramus. Its age is clearly the same 

 as that of the greater part of the White Limestone of Ireland and of 

 the highest beds of Chalk in England. 



The Estuarine series (III.) may be fairly regarded as representing 

 the whole or a portion of the Chalk series intervening between the 

 Upper Greens and on the one hand, and the Chalk with Belemnitella 

 mucronata on the other. 



The age of the Upper Estuarine series (I.) is more donbtful. It 

 appears to be so closely connected with the series below, that I am 

 strongly inclined to regard it as of Cretaceous age, and either as 

 representing one of the higher members of the Chalk (the Eaxoe or 

 Meudon beds) not elsewhere developed in this country, or as depo- 

 sited in the interval between the Cretaceous and Eocene periods. 

 But it is by no means impossible that future research may demon- 

 strate these beds to belong to the Tertiary and to be of Eocene or 

 even later date. 



Thus we have arrived at the conclusion that while the series IV. 

 represents the Upper Greensand ; III., II., and I. must in all 

 probability be regarded as constituting an abnormal development of 

 the English Chalk. It will be convenient to discuss the characters 

 of these two sets of deposits separately, 



In the northern portion of the Western Highlands no trace of the 

 Cretaceous strata has yet been detected ; and, indeed, the whole of 

 the strata show a tendency to thin out in that direction. We must 

 not, however, overlook the possibility that beds of this age may once 

 have existed there and have been wholly removed by denudation ; 

 and this caution will more especially appear to be necessary when we 

 remember the deposits of chalk-flint in Aberdeenshire, which seem 

 to prove the extension of the Cretaceous ocean in that direction. 



a. The Upper Greensand and associated Beds. 



Perhaps the best exposures of the Upper-Greensand strata are 

 those which occur about Carsaig, on the south side of the island of 

 Mull ; and it is here that I first detected the presence of beds of this 

 age in 1872. 



Above Carsaig House, and in the midst of woods that clothe the 

 precipices which shelter this beautiful spot, there is an old quarry, 

 from which, when the house was originally built, masses of stone 

 were thrown down for burning into lime. This stone is found to 

 be crowded with fossils of the Upper Greensand, Exogyra conica 

 occurring in the greatest profusion, and Pecten orbicularis being by 

 no means rare. 



The section here is by no means clear or well exposed. At two 

 separate points I have detected masses of the altered chalk- and flint- 

 beds squeezed out from beneath the mass of superincumbent basalt ; 

 but further than the fact that these beds overlie the Greensand, it is 

 impossible to obtain any light on the true relations of the members 

 of the Cretaceous series here. The section (fig. 10) shows the general 

 relations of the beds exposed in the cliffs at Carsaig. 



