NOTES. 305 



similar fishes and plants, reposed, near Kirkwall, the capital 

 of the Orkneys, upon a lower red sandstone, — the rock, in 

 fact, out of which the beautiful cathedral of that town is 

 built, — and are surmounted in several of the islands by an- 

 other sandstone, usually of light and yellowish colour, but 

 with some admixture of red, the most splendid natural view 

 of which is at Hoy Head. There the sandstone overlying 

 the Caithness flags has a vertical thickness in the sea-cliff of 

 1100 feet ! The entire succession of the group is thus seen 

 in Pomona and Hoy." 



Note C, p. 21. 



We have in the prefatory remarks adverted to the many 

 and quite irrefmgable proofs that members of the Cephalas- 

 pian family are the fish which at the present moment are 

 found to occur in the earliest formations. Geologists resid- 

 ing on the formations where they are found ought by all 

 means to devote themselves to the completion of all the parts 

 of these interesting fishes. One of the first descriptions given 

 of it, which, however, may be regarded as descriptive of mere- 

 ly its appearance in the stone, is to be found in the Old Red 

 Sandstone, from which we quote : — 



" The Cephalaspis is one of the most curious ichthyolites of the sys- 

 tem (the Comstone formation). Has the reader ever seen a saddler's 

 cutting knife, — a tool with a crescent-shaped blade, and the handle fixed 

 transversely in the centre of its concave side 1 In general outline the 

 Cephalaspis resembled this tool, — the crescent-shaped blade representing 

 the head, —the transverse handle the body. We have but to give the 

 handle an angular instead of a rounded shape, and to press together th« 

 pointed horns of the crescent till they incline towards each other, and the 

 convex or sharpened edge is elongated into a semi-ellipse, cut in the line 

 of its shortest diameter, in order to produce the complete form of the 

 Cephalaspis. The head, compared with the body, was of great size, 



U 



