Dr. R. H. Traquair—Old Red Sandstone Fishes. 507 
granites, including among their constituents microcline and horn- 
blende, the felstones, the diorites and other types of igneous rock, 
and the argillite, are all in close relation to the specimens already 
described from Socotra.! 
IX.—Norrs on tHe NoMENCLATURE OF THE FISHES OF THE OLD 
Rep Sanpstone oF Great Britain. 
By Dr. R. H. Traquair, F.R.S., F.G.S. 
HE nomenclature of the fishes of the Old Red Sandstone of Great 
Britain, with the exception of the Cephalaspide, revised some 
years ago by Professor Lankester, is at present in a very unsatisfac- 
tory state. A vary large number of the species named by Agassiz, 
as well as by McCoy, were undoubtedly founded upon deceptive 
characters, due partly to different modes of preservation in different 
rocks, partly also to those apparent variations in external form, 
which are inevitable in such ancient fossil fishes devoid of a fully 
ossified internal framework, without which the original outline can- 
not be expected to be constantly preserved. In specimens from one 
locality the external ganoid surface of the scales may be well shown, 
in those from another it may be constantly hidden or obscured, 
while the proportional measurements in the very same species may 
vary infinitely, by the fish being lengthened out, or shortened up 
by changes, which have occurred after death or during the consolida- 
tion of the enclosing rock. These and kindred sources of fallacy 
can only be guarded against by long experience in deciphering such 
remains, coupled with the examination of an immense number of 
specimens. 
As I am at present engaged on a complete synonymic Catalogue of 
the Paleozoic Ganoids and Dipnoi in the Kdinburgh Museum, I 
shall limit myself in the following brief ‘‘ notes” to indicating a few 
of the principal results which I have obtained in the course of my 
examination of the fishes of the Old Red Sandstone. 
Order Drpnot. 
Family Diererip (Ctenodipterini, Pander). 
Dipterus, Sedgw. and Murch.—Four species of this genus were 
named by Sedgwick and Murchison, namely, D. macropygopterus, D. 
brachypygopterus, D. Valenciennesii and D. macrolepidotus. All four 
were united by Agassiz under the name of macrolepidotus, but it 
was clearly shown by Pander and McCoy that macrolepidotus had 
no place in the original definition of the genus, being possessed of 
rhombic instead of circular scales. The other three were maintained 
to be distinct by McCoy, while Sir Philip Egerton, admitting the 
identity of the first two, still held out for the separation of Valen- 
ciennesti. After a careful study of the original types in the collec- 
tion of the Geological Society I fully agree with Pander that D. 
macropygopterus, brachypygopterus, and Valenciennesii are one species, 
for which it is desirable to retain the last-mentioned name, given in 
1 Phil. Trans. 1883, p. 273. 
