DESCRIPTION OF THE FOSSIL REMAINS. 51 



matrix, in their full rounded forms, cand each a third part of 

 their natural sizes. The large caudal system of fins in Plate 

 VIII. fig. 1, is nine inches and a quarter in length, and five 

 inches and nearly a half in breadth, and, adjoined to the 

 holoptychius in Plate VII., renders the restored length of that 

 magnificent specimen to be about forty-two inches. The 

 greatest breadth in the anterior part of the body is fully 

 thirteen inches and a half. In both, the pictorial effect, which 

 was chiefly aimed at, is finely brought out according to Nature's 

 own arrangement in her enduring and faithful lithograph. 



The fishes of the Old Red Sandstone formation all belong to 

 the placoid and ganoid order's ; and their families are repre- 

 sented by the lepidoids, the sauroids, and cselacanths. The 

 fossil remains of Dura Den fall to be arranged under these 

 natural divisions, and furnish of their several kinds perhaps 

 the best specimens, in perfect outline and preservation, that 

 have anywhere been detected in the rocks of the earth. " Geo- 

 logy demonstrates," says Professor Owen, " that the creative 

 force has not deserted this earth during any of her epochs of 

 time ; and that in respect to no one class of animals has the 

 manifestation of that force been limited to one epoch. Not a 

 species of fish that now lives, but has come into being during a 

 comparatively recent period : the existing species were pre- 

 ceded by other species, and these again by others still more 

 different from the present. No existing genus of fishes can be 

 traced back beyond a moiety of known creative time. Two 

 entire orders (cycloids and ctenoids) have come into being, and 

 have almost superseded two other orders (ganoids and placoids) 

 since the newest or latest of the secondary formations of the 

 earth's crust."* 



* Address by Richard Owen, V.P.R.S., to the British Association at Leeds, 1858. 



