152 PKOCEEDIXGS OE THE GEOLOGICAL SOCIETY. [Jan. 8, 



sufficiently exact character for fixing the age of the beds ; but from 

 the resemblance in penological characters of the strata exposed at 

 Dunrobin to those near Brora, he was led to regard the former as a 

 mere repetition of the latter, and therefore of Lower-Oolite age. In 

 later years Sir Roderick Murchison obtained specimens of Hippopo- 

 dium ponderosum, Sow., from the Dunrobin shore, and was thus led 

 to the recognition of the fact that strata of Liassic age exist there *. 



The two patches of strata which were in 1826 referred to the Lias 

 by the same author as the result of a confessedly somewhat hasty 

 examination f, and which have since been almost uniformly so re- 

 garded by geologists in Scotland, will be shown in this memoir to be 

 of the age of the Coralline Oolite and the Kimmeridge Clay re- 

 spectively. 



With regard to the marine strata, which form the upper part of 

 the series we have been describing as occurring at Dunrobin, there is 

 fortunately no room for doubt as to the question of their position in 

 the geological scale. An inspection of the list of fossils will show 

 that the beds which yield them undoubtedly belong to the Lower 

 Lias, and to that part of it which Quenstedt has distinguished as the 

 Lias j3. This is the highest portion of the Lower Lias according to 

 the classification usually adopted on the Continent, but its middle 

 portion according to the English method of grouping the beds. 



The fauna of these beds at Dunrobin is not without some ano- 

 malous characters, some of which, such as the rarity and small size 

 of the Cephalopoda, the dwarfed condition of the Oysters, and the 

 absence of Echinoderms and of many of the species of Mollusca 

 usually found at this horizon, may be accounted for on the ground 

 that the beds were probably deposited under less favourable condi- 

 tions than their typical equivalents in England and Swabia. These 

 unfavourable conditions would appear to have been the shallower 

 and less tranquil state of the sea, and possibly also the colder 

 climate. Certain other of the peculiarities, as for example the asso- 

 ciation in the same bed of species which in Swabia characterize di- 

 stinct but contiguous horizons, must be referred to the fact that the 

 beds were deposited in a remote locality, and that the character of 

 the fauna would thus be influenced by the varying migrations of 

 some, and the unequal persistence and gradual extinction of other 

 species. Nevertheless, in spite of these minor peculiarities, no one 

 acquainted with the association of Jurassic species in England, 

 Northern France, and Western Germany, can hesitate to regard 

 these beds in the north of Scotland as the deposits of a portion of 

 the same great sea, and as included within the same ancient province 

 of marine life. 



Having thus, by means of the beautiful marine fauna of its higher 

 beds, fixed the newer limit of age of the series of estuarine beds at 

 Dunrobin, the base of which is formed by deposits certainly Triassic, 

 and others probably Rhaetic, we can have little hesitation in regard- 



* See First Sketch of a Geological Map of Scotland, 1861 ; also Quart. Journ- 

 Geol. Soc. vol. xv. (1859) plate xii. 

 t Trans. G-eol. Soc. 2nd ser. vol. ii. part 2, p. 307. 



