318 Siluria—Present State of Geology. 
the trace of a fish amid the miultitudes of all other marine beings in 
the various sediments which constitute the chief mass of the Silurian 
rocks. Of these, though they are the lowest in the scale of the 
great division vertebrata, we are unable to perceive a vestige until 
we reach the highest zone of the Upper Silurian, and are about 
to enter upon the Devonian period. Even on that horizon the minute 
fossil fishes, long ago noticed by myself, are exceedingly scarce, 
and none have since been found in strata of higher antiquity, In 
fact the few fragments of cartilaginous ichthyolites of the highest 
band of Silurian rock still remain the most ancient known beings of 
their class. 
“‘ Looking, therefore, at the Silurian system as a whole, and 
judging from the collection of facts gathered from all quarters of the 
globe, we know that its chief deposits (certainly all the lower and 
most extensive) were formed during a long period, in which, while 
the sea abounded with countless invertebrate animals, no marine: 
vertebrata had been called into existence. The Silurian (except at 
its close) was, therefore, a series in which there appeared no example 
of that bony framework of completed vertebrae from which, as ap- 
proaching to the vertebrate archetype, the comparative anatomist * 
traces the rise of creative power up to the formation of man. 
“‘ Whether, therefore, the term of ‘ progressive’ or that of ‘ suc- 
cessive’ be applied to such acts of creation, my object is simply to 
show, upon clear and general evidence, that there was a long period 
in the history of the world wherein no vertebrated animal lived. In 
this sense, the appearance of the first recognizable fossil fishes is as 
decisive a proof of a new and distinct creation as that of the placing 
of man upon the terrestrial surface at the end of the long series of 
animals which characterize the younger geological periods. : 
_ © Nor have we been able to disinter from the older strata of this 
long period of invertebrate life any distinct fragments of land plants. 
But just in the same stratum wherein the few earliest small fishes 
have been detected, there also have we observed the first of a dimi- 
nutive, yet highly organized, tree vegetation. } 
“If it be granted that the position of the earliest recognizable 
* “See Owen on the Homology of the Vertebrate Skeleton, Reports Brit. Assoc. 
Adv. Sciences, 1849, p. 169. The general reader will find a powerful essay, 
embodying the opinions of the same high authority, on the proofs of a progres- 
sion in creation, Quarterly Review, 1851, p. 412, et seg. The arguments there 
employed have been strengthened by subsequent discoveries alluded to in this 
volume. I would also specially refer the reader to Professor Sedgwick’s Dis- 
course on the Studies of the University of Cambridge, for a masterly and elo- 
quent illustration of several of the views which are here advocated.” 
t Sir Roderick has long known the existence of bitumen and anthracite in 
the oldest greywacke or the Longmynd rocks, and considers that these sub- 
stances might have been derived from masses of sea-weed; and it appears that 
Professor Nicol detected, under the microscope, a tubular fibrous structure in 
the ashes of anthracite. Anthracite has been discovered in the old greywacke 
of Cavan, Ireland, by Mr John Kelly. 
