But of color, as I have said, though thus important, the ichthyologist can learn almost nothing from Geology. The perfect restoration of even a Cuvier are blank outlines. We just know by a wonderful accident that the Siberian elephant was red. A very few of the original tints still remain among the fossils of our north country Lias. The ammonite, when struck fresh from the surrounding lime, reflects the prismatic colors, as of old; a huge Modiola still retains its tinge of tawny and yellow; and the fossilized wood of the formation preserves a shade of the native tint, though darkened into brown. But there is considerably less of color in the fossils of the Old Red Sandstone. I have caught, and barely caught, in some of the newly disinterred specimens, the faint and evanescent reflection of a tinge of pearl; and were I acquainted with my own collection only, imagination, borrowing from the prevailing color, would be apt to people the ancient oceans, in which its forms existed, with swarthy races exclusively. But a view of the Altyre fossils would correct the impression. They are enclosed, like those of Cromarty, in nodules of an argillaceous limestone. The color, however, from the presence of iron, and the absence of bitumen, is different. It presents a mixture of gray, of pink, and of brown; and on this ground the fossil is spread out in strongly contrasted masses of white and dark red, of blue, and of purple. Where the exuviæ lie thickest, the white appears tinged with delicate blue--the bone is but little changed. Where they are spread out more thinly, the iron has pervaded them, and the purple and deep red prevail. Thus the same ichthyolite presents, in some specimens, a body of white and plum-blue attached to fins of deep red, and with detached scales of red and of purple lying scattered around it. I need hardly add, however, that all this variety of coloring is, like the unvaried black of the Cromarty specimens, the result, merely, of a curious chemistry. CHAPTER XIV. The Cornstone Formation and its Organisms.--Dwarf Vegetation.--_Cephalaspides._--Huge Lobster.--Habitats of the existing Crustacea.--No unapt representation of the Deposit of Balruddery, furnished by a land-locked Bay in the neighborhood of Cromarty.--Vast Space occupied by the Geological Formations.--Contrasted with the half-formed Deposits which represent the existing Creation.--Inference.--The formation of the _Holoptychius_.--Probable origin of its Siliceous Limestone.--Marked increase in the Bulk of the Existences of the System.--Conjectural Cause.--The Coal Measures.--The Limestone of Burdie House Conclusion.