268 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [ Mar. 25, 



The low land consists of pale brown and bluish clay-slate, in- 

 cluding subordinate layers of hard, yellowish, sometimes micaceous, 

 sandstone : in the clay-slate organic remains are exceedingly rare, 

 whilst in some of the layers of sandstone they are extremely numerous, 

 the same species being generally grouped together. Messrs. Morris 

 and Sharpe have kindly undertaken to describe these fossils in a sepa- 

 rate notice : they consist (as I am informed by them) of three new 

 species of Orthis, which have a Silurian character ; three of Spirifevy 

 which rather resemble Devonian forms, and approach closely to some 

 of the Australian species described by Messrs. G. B. Sowerby and 

 J.Morris*; one species both oi Atrypa and Choneles,i\ie latter ap- 

 proaching very closely some of the varieties of C. sarcinulata of 

 Europe ; an Orbicula and an Avicula, the species not determinable ; 

 and lastly, a fragment of a Trilobite and numerous traces of Crinoi- 

 dea, apparently related to the genus Actinocrinus. The concurrence 

 of these several organic forms in this remote part of the southern 

 ocean, giving to the aggregate so close a general resemblance with 

 the palaeozoic groups of the north, is an interesting circumstance. 

 None however of the species appear absolutely identical with north- 

 ern forms, or with the Silurian and Devonian mollusca described by 

 M. A. d'Orbigny from the Bolivian Cordillera ; these latter, eleven 

 in number, are likewise all distinct from, though several are most 

 closely related to, northern forms : two crustaceans however and a 

 Graptolite appear to be identical with European species. With re- 

 spect to the thirty-four or thirty-five palaeozoic mollusca from Au- 

 stralia!, Mr. Morris has come to the conclusion that all are new, 

 with the exception of one Terebratula : some of the species, more- 

 over, have required the institution of new genera. Mr. Lonsdale 

 has likewise found that the palaeozoic Australian corals are almost 

 all new species. Although the frequent and close general resem- 

 blance of the palaeozoic fossils in very distant parts of the world is 

 extremely remarkable, especially when we compare intra- and extra- 

 tropical districts (as in the case of those described by M. d'Orbigny), 

 yet I conceive that the opinion, that the further we look back in 

 time, the more widely distributed the same species of shells were, 

 must be greatly modified. 



We should bear in mind, that at the present day shells inhabiting 

 seas, which instead of being divided by impassable barriers of land 

 stretching north and south, are bordered by coasts running east and 

 west or are interspersed with islands, often have enormous ranges : 

 Mr. Cuming informs me, that he has upwards of a hundred species 

 of shells from the eastern coast of Africa identical with those col- 

 lected by himself at the Philippines and at the eastern coral-islands 

 of the Pacific Ocean : now the distance from these islands to Eastern 

 Africa is equal to that from pole to pole. Under similar circum- 

 stances Dr. Richardson has found that fishes have immense ranges. 

 Moreover we should bear in mind, how few genera of shells are 

 confined to particular regions of the world, that is, if we compare 



* Strzelecky's Physical Description of New South Wales, &c., p. 279 et seq. 

 f Strzelecky, ante cit., and the Appendix to C. Darwin's "Volcanic Islands. 



