442 
ELEMENTS OF GEOLOGY. 
Fig. 497. 
the same species which have a wide range in space are also 
the most persistent in time, which may prepare ns to find 
that some plants having a vast geographical range may also 
have endured from the period of the Upper Devonian to that 
of the Millstone Grit. 
Outliers of the Upper “ Old Red ” occur unconformably on 
older members of the group, and the formation represented 
at Whiteness, near Arbroath, a. Fig. 55, p. 74, may probably 
be one of these outliers, though the want of organic remains 
renders this uncertain. It is not improbable that the beds 
given in this section as Nos. 1, 2, and 3, may all belong to 
the early part of the period of the Upper 
Old Red, as some scales of Holoptychius 
nohilissimus have been found scattered 
through these beds. No. 2, in Strathmore. 
Another nearly allied Holoptychius occurs 
in Dura Den. A figure of this fish is an¬ 
nexed (Fig. 498), and also one of its scales 
_ (Fig. 497), as these last are often the only 
^( 2 ^QoiB.oio%>tycUu 8 no- parts met with; being scattered in Forfar- 
uiis%ymus,K^ Clash- g^ire through red-colored shales and sand- 
stones, as are scales oi a large species ot 
tie same genus in a corresponding matrix in Herefordshire.* 
The number of fish obtained from the British Upper Old Red 
Sandstone amounts to fifteen species referred to eleven genera. 
Fig. 498. 
d 
Holoptychius, as restored by Professor Huxley. 
a. The friuged pectoral fins. h. The fringed ventral fins. c. Anal fin. 
d, e. Dorsal fins. 
Sir R. Murchison groups with this upper division of the 
Old Red of Scotland certain light-red and yellow sandstones 
and grits which occur in the northernmost part of the main¬ 
land, and extend also into the Orkney and Shetland Islands. 
* Siluria, 4th ed., p. 265, 
