﻿446 Charles Callaway — Migration of Bpecies. 



of the Mollusca are the most important. This is emphatically the 

 case with the older PalEeozoic fossiliferous groups, in which molluscs 

 are the predominant forms of life. Brachiopoda, especially, abound 

 in all epochs, from the Cambrian to the Carboniferous, 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 

 Palaeozoic 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 Palaeozoic 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 

 think, 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 Parr}', Franklin, Belcher, 

 and others, and examined by Salter, were shown to be chiefly from 

 Silurian limestones. Fossils recently collected by Captain Fielden 

 during the Arctic Expedition (which, through the kindness of Mr. 

 Etheridge, I have been permitted to examine) throw additional light 

 upon this point, and prove the interesting fact that within 450 miles 

 of the Pole there flourished a molluscan and coralline fauna closely 

 similar to that contained in British and North American Palseozoic 

 limestones. It is, therefore, 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 

 climate. 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 be 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 keep in mind that faunas and floras are not in the habit 



