15. PREFATORY REMARKS 



Lower Old Red Sandstone ; but it there comes to an end, so far 

 as we know. Other ichthyic forms, however, appear in that 

 creation, binding together the Lower system with those that 

 follow. The lepido-ganoids of Owen appear m tha shape 

 chiefly of the Acanthodes, which, however, differ specifically 

 from those of Cromarty and CaithnesB (the Middle Old Kedit 

 This discovery of the Acanths, &c., as contemporaries of the 

 Cephalaspis, has but very recently taken place, and was un- 

 known to Hugh Miller. They likewise are not signs, but 

 things, so very plain that a child may take delight in ex 

 amining them. 1 have seen some in the collection of Mr 

 Powrie of Reswallie, of which the minute and beautiful scales, 

 the fins, the hungry-looking open jaws full of hooked teeth, 

 may be all microscopically examined. And the ocean of the 

 Lower Old Red seems to have swarmed, too, with its finny 

 inhabitants. 



The Rev. Hugh Mitchell of Craig, near Montrose, — a 

 most successftd collector in this new field, — ^thus writes me : 

 — " Over a wide district we have detected the indications 

 of an extensive fossil fauna, and even flora. Cephalaspis 

 Lyelli used to be the only complete form of fossil fish known 

 from our rocks ; but, besides another species of Cephalaspid. 

 we possess complete forms of Acanthodes, — Climaiius and 

 Diplacanthus. 



" We have, besides, with the single exception of the Pteras- 

 pis, found all the species recorded from the equivalent rocks 

 in England, which are either named from spines, such as 

 Onchus, Ctenacanthus, or from jaws with anchylosed teeth, 

 such as Plectrodus. But we have many, very many unnamed 

 spines and scattered scales, which indicate many discoveries yet 



