Murchison’s Siluria. 381 
enormous that, as Hall justly remarks,* “the small number of re- 
stricted species reduces the importance of the system to the value 
of some of our subordinate groups.” D’Orbigny, however, con- 
siders that the great number of species heretofore considered iden- 
tical is due solely to incorrect determinations. 
here in England the line between Upper and Lower Silurian 
shall be drawn is another question which seems by no means sat- 
isfactorily settled, although Murchison remarks that “it was at 
the summit of this Caradoc sandstone that I long ago drew the 
line of demarkation between the inferior and superior masses of 
the Silurian systems and observations extended to many distant 
regions have confirmed the general truthfulness of that division.” 
In the original classification of the Silurian by Murchison, the 
Caradoc and Llandeilo groups were bracketed together as Lower 
Silurian, and in the Siluria we are reminded that all the fossils 
which most frequently occur in the heart of the Caradoc forma- 
tion are found in the Llandeilo, and yet the Government Survey- 
ors have decided that the Caradoc must be taken from the Lower 
Silurian and placed as an intermediate group between that and the 
pper division, at the same time allowing that the two cannot 
be palzontologically separated from each other. Sedgwick and 
M’Coy have shown that the rocks colored as Caradoc in the Mal- 
vern Hills by the Government Survey are filled with Wenlock 
ossils. Partly as a result of this confusion, we find figured in 
the Silnria, as characteristic of the Lower Silurian a number of 
ossils which in this country are universally recognised as Upper 
Silurian only; for instance, merus oblongus, Halysites ca- 
ae (Catenipora escharoides), Favosites Gothlandica and 
others. 
The map attached to the Siluria, on which is represented the 
* Foster and Whitney’s Report, Part II, p. 312. 
