1873.] JTTDD THE SECONDARY ROCKS OP SCOTLAND. 169 



nodules of argillaceous ironstone, containing Belemnites Owenii, Pratt 

 (abundant), Ammonites (crushed specimens). 



(b) Somewhat more sandy clays ; very imperfectly seen. 



(c) Thick beds of blue, somewhat sandy shale, with some bands of argilla- 



ceous limestone and septaria. Fossils are not abundant : Gryphcea 

 dilatata, Sow., (small variety) ; Belemnites Owenii, Pratt. 



(d) " Eoof-bed " of the Coal. 



The great sandstone series between these clays and those repre- 

 senting the Coralline Oolite does not appear to be present at Cadh'- 

 an-Bigh. It is probable that by a small transverse fracture the 

 " Ornatus-clays " of this place are thrown against the clays of the 

 Coralline Oolite of Port-an-Bigh. 



C. Zone of Ammonites perarmatus, Wright. — The thick series 

 of beds, with predominating argillaceous characters, which rests 

 upon the roof-bed of the coal, is surmounted by, and passes up into 

 a mass of fine-grained argillaceous sandstones, with marine fossils 

 tolerably abundant, especially in its upper portion. These marine 

 sandstones, which are about 25 feet thick, are well seen on both 

 sides of the river Brora ; on the right bank the beds are presented 

 in two exposures, being bent over in an anticlinal, the dip being N. 

 at 12° and S. at 8°. At this point the strata consist of very fine- 

 grained brittle sandstone of a yellowish colour, mottled with streaks 

 of grey. Occasionally certain layers and concretionary patches are 

 found converted into an intensely hard compact quartzite-like rock, 

 with a fine conchoidal fracture. 



In these beds fossils are tolerably abundant, but almost always 

 in the condition of casts, and frequently much distorted by pressure. 

 The species which especially characterizes these beds by its great 

 abundance is a Lucina, which was confounded by Sowerby with his 

 Lucinct crassa, a JNeocomian form. "Wood, sometimes in very large 

 masses and always more or less crushed, abounds in these sand- 

 stones. Ammonites, Belemnites, Pectens, and other bivalves occur 

 by no means rarely in these beds. The list of their fossils is as 

 follows : — 



Ammonites cordatus, Sow. 



Sutherlandise, Sow. 



excavatus, Sow. 



perarmatus, Sow. 



, sp. 



Belemnites sulcatus, Mill. 



Owenii, Pratt. 



Gryphtea dilatata, Sow., var. 

 Exogyra nana, Sow., sp. 

 Pecten fibrosus, Sow. 



Pecten vimineus, Sow. 



vagans, Sow. 



demissus, Phil. 



, sp. 



Pinna lanceolata, Sow. 

 Lucina (crassa, Sow., pars). 

 Goniomya v-scripta, Sow., i 

 Pholadomya, sp. 

 Wood. 



On comparing this list of fossils with that from the clays below, 

 we find that we have entered a new zone of life. The Ammonites of 

 the group of the Ornati have wholly disappeared, and have been re- 

 placed by those of the group of the Cordati — those of the groups of 

 the Armati and Planulati persisting, but being represented by other 

 species. Among the Belemnites, B. Owenii, Pratt, and its varieties 

 are here very rare, while B. sulcatus, Mill., has greatly increased in 



