446 Charles Callaway — Migration of Species. 
of the Mollusca are tbe most important. Tliis is empliatically the 
case with the older Palasozoic fossiliferous groups, in wliich molluscs 
are the predominant forms of life. Brachiopoda, especially, abound 
in all epoclis, from the Cambrian to the Carbouiferous, and are most 
valuable for our purpose. Molluscous faunas are of very wide dis- 
tribution even in the present day. Dr. Krauss informs us that 
Banella granifera ranges from the Eed Sea to New Zealand, Purpura 
lapillus from Greenland to the Cape, Venus verrucosa from Britain to 
the Cape. Dr. S. P. Woodward (Manual Moll. p. 60) states that, 
“ out of 270 sea-shells found on the coast of Massachusetts north of 
Cape Cod, more than half are common to Northern Europe.” In 
wider seas, species have a still greater extension. In the great 
Indo-Pacific province, including “ three-fifths of the circumference 
of the globe and 45° of latitude,” the facies of the fauna is uniform. 
“ Mr. Cuming obtained more than 100 species of shells from the 
eastern coast of Africa, identical with those collected by himself at 
the Philippines, and in the eastern coral islands of the Pacific.” In 
Palasozoic times, the conditions for the extension of species were 
undoubtedly more favourable than in most recent provinces; and, in 
all probability, closely resembled the conditions now prevailing in 
the Indo-Pacific province. That resemblance is seen chiefly in two 
points : in freedom from extremes of temperature, and in continuity 
of marine conditions. In proof of the latter point, it will be neces- 
sary to show that the sea was open from the eastern to the Western 
hemisphere in Palmozoic times. It is highly probable that the 
Southern part of what is now the northern Atlantic was occupied by 
Continental land ; but that the sea was open towards the north will, I 
thiuk, be evident from the following considerations. The Middle 
Silurians (Murchison) of New York and the Appalachians (Oneida 
Conglomerate and Medina Sandstone) are represented towards the 
north-east, in Anticosti, by a continuous series of marine limestones. 
The fossils collected in Arctic regions by Parry, Franklin, Beicher, 
and others, and examined by Salter, were shown to be chiefly from 
Silurian limestones. Fossils recently collected by Captain Fielden 
during the Arctic Expedition (wliich, through the kindness of Mr. 
Etheridge, I have been permitted to examine) throw additional light 
upon tliis point, and prove the interesting fact that within 450 miles 
of the Pole tliere flourished a molluscan and coralline fauna closely 
similar to that contained in British and North American Palseozoic 
limestones. It is, tlierefore, highly probable that British and 
American seas communicated with each other by way of the 
northern part of the North Atlantic. Lying in the same latitudes, 
both eastern and Western areas must also have been similar in 
cliinate. We may, then, safely infer that, as in the present day a 
similar fauna extends continuously for 15,000 miles in open seas, 
the same animals lived at the same time in British and North 
American seas. If this he so, identity of species is not a proof of 
non-contemporaneity, and the orthodox doctrine of the value of 
fossils as indices of contemporaneity is the true teaching. 
We must lceep in mind that faunas and floras are not in the habit 
