THK JURASSIC SYSTKM 403 



revealed the fact that a similar succession of beds existed there in 

 Tertiary times, for in the conglomerate which fills a large volcanic 

 orifice or neck (see p. 368) fragments and tabular masses of Rhu^tic 

 and Liassic limestones were discovered, the fossils found in them 

 leaving no doubt about the age of the rocks. 



Farther north on the coast of Argyleshire and in the islands 

 of Mull, Skye, and Raasay, a nearly complete succeasion of Liassic 

 (i<pn~it- is found, which differ in several respects from those of 

 England. They were fully described by Professor Judd in 1878, 9 

 from wh'ose account the following is mainly taken. 



The Rhaetic zone is thin and seems to be represented by about 

 8 feet of calcareous sandstones, limestones, and shales. The over- 

 lying beds are very hard bluish-grey limestones, alternating with 

 calcareous grits and conglomeratic sandstones. The commonest 

 fossil is Ostrea irregularis (a variety of 0. liassica), but corals Thecos- 

 milia Martini and Isastrea Murchisoni also occur, together with 

 Cardinia concinna and spines of Acrosalenia. Ammonites are not 

 found, but the beds may be regarded as equivalent to the planorbe 

 and angulatum zones ; their thickness is about 200 feet, and they 

 are well seen at Applecross and on the opposite coast of Raasay 

 (see Fig. 132). 



The succeeding zone of Arietites Bucklandi is well developed, and 

 consists of shelly limestones and shales crowded with fossils of the 

 same species which are common in England ; its thickness is 250 

 feet. Above are dark micaceous shales containing Arn. semicostatum, 

 Asteroceras Brooki, and Belemnites acutus, 150 feet. The separate 

 existence of the oxynotum zone is not determined, the fossils of 

 this zone only occurring at Tobermory in Mull, where they are 

 mingled with others that belong to higher horizons. 



The higher part of the Lower Lias consists of sandy and 

 micaceous shales called the Pabba shales by Professor Judd. At 

 the base of these there are some beds in which Deroceras armatum 

 occurs, but the greater portion of the group represents the zones 

 Jamesoni and capricornus ; these shales contain Uptonia Jamesoni, 

 Platypleuroceras brevispina, Deroceras Dav&i, Modiola scalprum, and 

 Gryphcea cymbium, and are about 250 feet thick. 



In the north-east of Scotland beds of Liassic age occur in the 

 reefs below Dunrobin Castle on the Sutherland coast. Here the 

 basement l)eds consist of coarse sandstones and conglomerates, con- 

 taining fragments of the cherty rock mentioned on p. 369. These 

 beds are succeeded by a remarkable set of estuarine deposits, 

 consisting of sandstones and shales with thin layers of clay and 

 coal, the whole attaining a thickness of between 400 and 500 

 feet ; no fossils have been found except in the uppermost beds, 



