1858.] MURCHisoiir — northern highlands, etc. 409 



trees, some of considerable size*, and, according to their minute 

 structure, of the Araucarian type ; Lejpidodendron also is rather 

 abundant, and a Lycojpodites occurs. It is but a scanty assemblage, 

 after all, as to species, but may be compared with that flora recently 

 detected by Prof. Dawson in the Devonian beds of Nova Scotia, where 

 Coniferce of a somewhat different type, and Lepidodendra, are the 

 chief forms described f. On the whole, it is analogous to that of the 

 Carboniferous formation, though distinct as to species. There were 

 large Coniferous trees — with whorls of branches, and with a struc- 

 ture like that of the Norfolk-pine ; also Lepidodendron, Lycojoodites, 

 and Ferns. That these grew liear the coast and were entombed in 

 the shallows of a muddy shore, seems proved by their good pre- 

 servation and from the coarse nature of the matrix, which is, 

 moreover, indented by the burrows of sea-worms, like those made 

 upon the shores in our own day. 



As we advance still higher in the series, or into the strata which 

 overlie the Caithness flags, other fossil plants of large size begin to 

 appear ; and several of these have been discovered in the Orkneys and 

 Shetlands by Mr. Tufuell and Dr. Hamilton, and belonging either to 

 Columnaria or to some allied genus, make an approach to forms 

 usually considered as characteristic of the Carboniferous era (p. 413). 



Upper Old Red of Caithness. — In various parts of the north coast 

 of Caithness the series of dark-coloured flagstones, nearly aU more 

 or less bituminous, is seen to graduate upwards into light-coloured 

 sandstone, in parts reddish, but usually of yellowish colours. At 

 Reay^, indeed, such sandstones are developed so very low in the series 

 (see Section, fig. 12, p. 404) as to be interlaced with some of the lowest 

 beds of flagstone. Here and there, as between the town of Thurso 

 and Holborn Head, a band of this character is intercalated higher 

 up among the flagstones, and the beds, being thicker and softer than 

 the associated flagstones, are used for building. 



Fig. 15. — Section showing the relations of the Caithness Flags to the 

 Upper Old Red Sandstone in the neighbourhood of Dunnet Head. 



Dunnet 

 S. Ham. Brough. Head. N. 



Caithness flags. Dpper Old Red Sandstone. 



In the bold promontory, however, of Dunnet Head, the observer 

 ascends from the flagstones as exhibited on the coast from BarrogiU 

 Castle to the fishing-villages of Ham and Brough, as represented in 

 the Section, fig. 15, where, after several undulations and breaks, 

 those dark bituminous and ichthyolitic beds are carried under the 



* A large carbonized stem similar to those first mentioned (p. 406) has recently 

 been discovered by Mr. Peach. It measured several feet in length by sixteen 

 inches in breadth, thus proving that these Old Red plants attained the dimen- 

 sions of large fir-trees. 



t Proceed. Geol. Soc. January 5, 1859. 



