184 THE CRUISE OF THE BETSEY ; OB, 



passed, it might be found retaining unbroken its gigantic pro- 

 portions. There was molten pitch poured over the bones in 

 a state of sufficient fluidity to permeate all their pores, and 

 fill up the central hollows, and which, soon hardening around 

 them, formed a bituminous matrix, in which they may lie un- 

 changed for more than a thousand years. Now, exactly such 

 was the process of keeping to which nature resorted with these 

 skeletons of the Old Red Sandstone. The animal matter 

 with which they were charged has been converted into a hard 

 black bitumen. Like the bones of the Bruce, they are bones 

 steeped in pitch ; and so thoroughly is every pore and hol- 

 low still occupied, that, when cast into the fire, they flame 

 like torches. In one of the beds at which we have now ar- 

 rived Mr Dick found the occipital plates of a Holoptychius 

 of gigantic proportions. The frontal plates measured full 

 sixteen inches across, and from the nape of the neck to a 

 little above the place of the eyes, full eighteen; while a single 

 plate belonging to the lower part of the head measures thir- 

 teen and a half inches by seven and a half. I have remarked, 

 in my little work on the Old Red Sandstone, founding on 

 a large amount of negative evidence, that a mediocrity of 

 size and bulk seems to have obtained among the fish of the 

 Lower Old Red, though, in at least the Upper formation, a 

 considerable increase in both took place. A single piece of 

 positive evidence, however, outweighs whole volumes of a 

 merely negative kind. From the entire plate now in my pos- 

 session, which is identical with one figured in Mr Noble of 

 St Madoes' specimen, and from the huge fragments of the 

 upper plates now before me, some of which are full five-eighth 

 parts of an inch in thickness, I am prepared to demonstrate 

 that this Holoptychius of the Lower Old Red must have been 

 at least thrice the size of the Holoptychius Nobilissimus of 

 Clashbennie. 



Still we pass on, though with no little difficulty, over the 



