1912-13.] Obituary Notices. 339 
Rocks of the Edinburgh District,” published in the Transactions of this 
Society in 1903. This paper contains the results of his work in this field 
extending over a period of thirty years. 
By means of the fish remains he arranged the Carboniferous rocks in 
two divisions — an upper and lower, drawing the boundary line about the 
horizon of the Millstone Grit. He found that the fish faunas varied in 
accordance with the type of sedimentation. Thus the fish remains occurring 
in the limestones of open sea origin are essentially different from those met 
with in the estuarine beds. The marine limestones of the Lower Carboni- 
ferous rocks yield mainly Elasmobranch forms ; Dipnoi and Ganoids being 
rare. On the other hand, the estuarine strata from the bottom to the top 
of the Carboniferous system are characterised not only by Dipnoi and 
Ganoids, but by a set of Elasmobranchs differing generically and specifically 
from those of the marine limestones. Every geologist must recognise the 
extreme importance of this deduction. 
He also discussed the question of the value of fossil fishes as zonal 
indices of stratigraphical horizons. He admitted that it was hardly possible 
to establish satisfactory life zones by means of the fishes in the Lower 
Carboniferous rocks, but he called attention to the remarkable divergence 
in the characters of the estuarine fish fauna on the south side of the 
Southern Uplands from that in the Midland Valley; and he speculated as 
to the probable influence of a land barrier in accounting for this divergence. 
He showed that in the estuarine beds of the lower division of the system 
many of the species must have lived for a long lapse of time without any 
change in their specific characters. But above the Millstone Grit he 
encountered a new fauna from which nearly all the Lower Carboniferous 
species and a number of the genera had disappeared. He held that the 
cause of this remarkable palaeontological break in the fish fauna was a 
question which specially concerned the geologist. 
In 1887 Dr Traquair began the detailed study of the fish fauna of the 
Old Red Sandstone, which led to an extensive revision of the nomenclature. 
Following the classification of Murchison and Salter, he arranged the strata 
of this formation in Scotland in three divisions — a lower, middle, and upper ; 
the sequence being determined by the assemblage of fish remains in each 
division. He pointed out the resemblance of the fish fauna in the 
formation south of the Grampians to that of the Lower Old Red Sandstone 
of the west of England and adjoining part of Wales, and to the Lower 
Devonian rocks of Canada. On the other hand, he showed that the Orcadian 
rocks north of the Grampians yield an entirely different fish fauna, which he 
grouped with the Middle Devonian. The third great fish fauna found in 
