MITCHELL — ACANTHODES IN PAL^IOZOIC ROCKS. 
131 
Scotland, in the summer of the year 1857. From investigations 
since made, it now appears that an abundant flush of Acanthodian 
life ushered in the morning of the vast period embraced by the Old 
Ked Sandstone. Along with the genus Acanthodes there occur also 
several other genera of the Acanthodian family, such as Climatius, 
Parescus, and some unnamed. The genera Climatius and Parescus 
were first founded upon and described by Agassiz, in his great work, 
from spines, but since the perfect forms have turned up in our 
northern rocks, it has been found necess;»ry to remove them from 
among the Cestraciont Placoids into the Acanthodian family of the 
Ganoids, that is to say, provided we adhere to the classification of 
Agassiz. Other genera and species occurring with us remain to be 
described, and we are very much disposed to think that the spines 
figured from the Ludlow bone-bed in tlie Upper Silurian must be 
relegated to Acanthodian forms. Much as has been made of it, have 
we any evidence of the occurrence of Placoidal fishes in those rocks 
at all, except pieces of shagreen-looking skin ? What if these, on 
closer scrutiny, turn out to be Crustacean and not Piscine remains ? 
Would it not be worth the while of some of the earnest observers in 
that region to examine carefully those Ludlow beds, or especially 
their equivalents, where spines occur, for the complete forms ? It 
was long thought that in our Scottish rocks of the Lower Devonian 
we had nothing but unattached spines of these fossil fishes. 
It may be observed, in order to remove all doubt of the position 
here assigned to the beds of the Old Ked Sandstone in which Acan- 
thodes first occurs, that we have specimens on the same slabs with 
plates of the Pterygotus, and in the same stone with Cephalaspis 
Lyellii. It may be that other species of Acanthodes occur in our 
Lower, but it is certain that in the Middle beds of the Old Eed, as 
they occur in ^loray and Caithness, there is a fuller development of 
species. But in such a feature the genus would resemble many otiiers 
in the geological muster-roll of being, — presenting us first with a 
weak dawn, — then culminating into meridian fulness, but again sink- 
ing into a slow decline and final extinction, yet still preserving 
throughout the career of their existence the characteristic traits of 
their generic life, the dying representative of the genus is not how- 
ever a degraded form, but is as beautiful and as highly a developed 
creature as its first introduced ally. The outline of the body of the 
Acanthodes of the Lower Devonian Egerton describes as remarkably 
graceful, and Komer has given the specific appellation of gracilis to 
the Acanthodes of the Lower Permian, 
It is certainly worthy of remark that the genus Acanthodes is per- 
sistent througirsuch a lengthened period of geological existence ; and 
from such a circumstance we are inclined to infer that as the details 
of the stony record are filled up, all gaps will disappear. We do not 
and cannot admit the truth of the theory of the transmutation ot 
species, yet the course of creation has not proceeded by sudden 
bounds, but by a steadv, calm advance. There is no evidence, so tar 
