714 



J. W. JUDD ON THE SECONDARY ROCKS OE SCOTLAND. 



of fossils from this locality. As they serve very "well to illustrate 

 the general fauna of the Seal pa beds, which here display their typical 

 mineral characters, consisting of more or less calcareous sandstones 

 and sandy shales, I have appended a list of the most abundant 

 species ; hitherto only some two or three species had been recorded 

 from the island in question : — 



Belemnites elongatus, Mill. 

 Ammonites spinatus, Brug. 



margaritatus., Be Montf. 



, varieties. 



Cryptsenia expansa, Sow. sp. 

 Pholadomya ambigua, Sow. 

 Avicula inasquivalvis, Sow. 

 Lima Hermanni, Ziet. 



acuticosta, Sow. sp. 



Pecten asquivalvis, Sow. 



sublsevis, Phil. 



liasinus, Nyst. 



, sp. 



Plicatula spinosa, Sow. 



leeviuscula, B'Orb. 



Gryphasa cymbium, Lam. 



gigantea, Sow. 



Ehynchonellatetrahedra,>Sow. sp. 

 — — bidens, Phil. sp. 



acuta, Sow. 



■ , sp. 



Terebratula resupinata, Sow. 



punctata, Sow. 



Pentacrinus robustus, Wr. 



The exposure of the Middle-Lias strata in the little island of 

 Pabba has often been described, and is justly celebrated on account 

 of the abundance of its fossils and the perfect condition in which 

 they are sometimes obtained. The dark brown micaceous shales 

 which compose the whole of this flat grass-covered island are well 

 exposed in the long shore-reefs, which are traversed by numerous 

 basaltic dykes that sometimes rise like great walls above the mouldered 

 masses of clay. Hugh Miller, in his graphic sketches of the geolo- 

 gical features of this district, was the first, after Macculloch, to 

 direct general attention to this rich storehouse of fossil remains ; 

 and, acting upon his suggestion, Professor A. Geikie made a consider- 

 able collection of the fossil forms occurring there, which were care- 

 fully catalogued (the new species being described, but not figured) 

 by Dr. T. Wright*. 



Although the Middle-Lias strata certainly occur at a number of 

 points in the district of Strath, in Skye, as under Beinn-na-Cailleach 

 in the north, and at Strathaird in the south, yet the proximity of 

 great igneous masses has resulted in such a vast amount of local 

 metamorphism that the fossils are almost everywhere obliterated, 

 and the characters and succession of the beds rendered exceedingly 

 obscure. 



Precisely the same remark applies to the exposures of Middle-Lias 

 strata in the district of Ardnamurchan, the next point southward 

 from Skye at which they appear. Here the rocks of this age are 

 usually metamorphosed so that no fossils are recognizable ; but the 

 order of succession of the strata, and an occasional fossil, enable us to 

 establish the fact that certain highly indurated shales and impure 

 limestones (the latter reduced to a highly crystalline condition through 

 the plexus of dykes by which they are intersected) really belong to 

 this part of the geological series. 



Thus, on the east of Xilhoan Bay we find sandy micaceous blue 



* Quart. Journ. Geol. Soc. vol. xiv. (1858), p. 24. 



