706 J. W. JTTDD ON THE SECONDARY EOCKS OF SCOTLAND. 



standing out from among the intervening crumbling shales in a 

 very striking manner. It is over one of the higher of these floors 

 of limestone that the burn of Hallaig tumbles into the sea, giving 

 rise to a very picturesque waterfall. The thickness of the Lower 

 Lias here cannot be less than 200 feet. At its upper part the sandy 

 argillaceous beds, containing peculiar forms of Gryphcea arcuata and 

 the Ammonites which characterize the Zone of Ammonites semi- 

 costatus, are found ; and these are seen to be directly overlain by the 

 shales containing the fossils of the Zone of Ammonites armatus. 



On the northern slope of Beinn Glamaig in Skye and along the 

 shores of Loch Sligachan the Lower-Lias and Infralias strata are 

 found thrown up at very high angles (from 32° to nearly vertical) ; 

 they are, however, frequently greatly altered by their contact with 

 the syenite, and their fossils are scarcely recognizable. 



The best sections of the Lower Lias in Skye are those exposed 

 along the shore of Broadford Bay, between Obe Breakish to near 

 the village of Broadford, at which latter place the Infralias strata 

 are brought up again by a fault. Here the succession of beds is as 

 follows : — 



Above the white sandstone and grit, passing into conglomerate, 

 which we regard as constituting the highest member of the Infra- 

 lias (though, as they contain no fossils, it may be equally allowable 

 to include them in the Lower Lias), we find a series of dark-coloured, 

 almost black micaceous shales, with only occasional limestone floors, 

 crowded with fossils, which occur both in the shales and limestones, 

 but most abundantly in the latter. The following species were ob- 

 served -.—Ammonites Bucklandi, Sow. ; A. Conybeari, Sow. ; Pleuroto- 

 maria similis, Sow. sp.; Gryphcea arcuata, Lam. ; Lima gigantea, Sow. 

 (normal form) ; Cardinia Listeri, Sow. ; Pecten textorius, Schloth. ; 

 Pecten, sp. ; Pinna Hartmanni, Goldf . ; Unieardium cardioides, Phil, 

 sp. ; Avicula sinemuriensis, D'Orb. ; and JSpiriferina Walcotti, Sow. 

 sp. These beds are probably at least 150 feet in thickness. 



This series of black, highly micaceous shales is continued upwards 

 by beds of precisely similar mineral character, which, however, con- 

 tain a slightly different fauna. The typical form of GrypJicea arcuata, 

 Lam., with a deep sulcus, is replaced by a variety of the same shell 

 far less conspicuously sulcated. The Ammonites allied to A. Buck- 

 landi, Sow., disappear ; and in their place we find very abundantly 

 Ammonites semicostatus, Y. & B., A. Sauzeanus, D'Orb., and several 

 other peculiar forms. The typical form of Lima gigantea, Sow., is 

 no longer found ; but in its place occurs a variety of greater flatness 

 than the type and of peculiar form. These beds evidently represent 

 the zone of Ammonites semicostatus. Their full thickness, however, 

 is not seen at Broadford Bay, as they are faulted against the Infralias 

 strata, which a little to the westward are quarried for lime-burning. 



Although the Lower-Lias strata are exposed at many other points 

 both in the interior and along the southern shore of the district of 

 Strath in Skye, yet they nowhere afford good sections. In many 

 places the strata are so altered, as in Strathaird and along the shores 

 of Lochs Eishart and Slapin, that scarcely a fossil can be recognized; 



