Vol. 63.] OF THE INTERIOR OOLITE OF BRORA. 381 



with the living one. The insecurity of argument based entirely on 

 the external morphology of plants is well known, and therefore it 

 is useful to have in these Brora specimens leaves which are so 

 well preserved that they show some microscopic detail. Judging 

 from them, it seems clear that Ginkgo cligitata is specifically dis- 

 tinct from G. biloba. 



In the introductory pages of Prof. Judd's paper, he says, of the 

 interesting patches of Jurassic rocks in the Highlands of Scotland, 

 that despite their fragmentary character we may 



' seek in them for the solution of many problems of the highest geological 

 interest, among which we may especially instance the following : — 



(1) The determination of the northern limits of the old life-province to 

 which we have referred, and the question whether the Scotch deposits 



were formed within it 



(3) The conditions under which the various beds constituting the Mesozoic 



Series in Scotland were deposited 



(5) The position and extent, with the nature and productions, of the lands 

 bounding this portion of the old Mesozoic sea.' (Op. tit. p. 100.) 



The bed of plants just recorded sheds its small ray of light on 

 these problems. The whole of the Oolitic deposits of the Brora 

 district consist of estuarine and marine beds abruptly alternating, 

 which as a rule contain very fragmentary remains of plants. The 

 bed in which these relatively well-preserved plants have been found 

 seems to have been formed under tranquil conditions, probably 

 in a lagoon of fresh or but slightly brackish water. There were no 

 animal-remains among the plants, except a single example of a 

 Unto, which was presumably a freshwater form : it could not be 

 specifically identified. The plants are those of a land-area, probably 

 with firm ground surrounding pools or shallow water, as seems 

 indicated by the fact that Ginkgo and Equisetites are the two 

 commonest forms ; these, with the ferns and other plants enume- 

 rated in the list on p. 378, certainly represent ' productions of the 

 lands bounding this portion of the old Mesozoic sea.' It is evident 

 that the flora of the Inferior Oolites of Brora is so similar to that 

 of Yorkshire as to* convince us that the plants of the Scottish 

 district belong to the same ' life-province ' as the one which in- 

 cluded Yorkshire during that period. 



Bibliographical List. 



W. Caeettthees (70). ' On Fossil Cycadean Stems from the Secondary Kocks of 



Britain' Trans. Linn. Soc. vol. xxvi (1870) pp. 675-708 & pis. liv-lxiii. 

 C. Fox Steangways (92). ' The Jurassic Rocks of Britain : vol. i — Yorkshire' 



Mem. Geol. Surv. 1892, pp. i-x, 1-551 & pis. i-vi. 

 J. W. Judd (73). 'The Secondary Rocks of Scotland' Quart. Journ. Geol. Soc. 



vol. xxix (1873) pp. 97-195 & pis. vii-viii. 

 H. Millee (62). 'The Testimony of the Rocks' Edinburgh, 1862. Lectures xi 



& xii (ed. 1869) pp. 383-454. 

 R. I. Muechison (27). ' On the Coal-field of Brora in Sutherlandshire . . . .' Trans. 



Geol. Soc. ser. 2, vol. ii (1827) pp. 293-326 & pis. xxxi-xxxii. 

 R. I. Mttechisoit (43). ' Observations on the Occurrence of Freshwater Beds in 



the Oolitic Deposits of Brora, Sutherlandshire ' Proc. Geol. Soc. vol. iv (1843) 



pp. 174-76. 



Q.J. G. S. No. 251. 2e 



