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the Trilol)ites and BrcaclaiDpoda occupied the most important place 

 iu the primordial fauna of oar globe, and if we excluded the proble- 

 matical Eozoon canadense from the animal creation, as some 

 natui'alists had done, we should find the Brachiopoda making their 

 first appeai-ance in the oldest known fossiliferous deposits, for Mr. 

 Hicks had obtained undoubted examples of Lingida or Lingulella, 

 (L. iirimoeva) from the very base of the whole Cambrian series of St. 

 Davids. They were less numerous during the Permian and Triassic 

 periods, while they again became abundant, although compai-atively 

 much less numerous, during the Jui-assic and Ci-etaceous times. 

 In the Tertiary period they had materially decx'eased in number, and 

 wei"e represented at the present time by about one hundred species. 

 But what wonderful changes had been operating during the in- 

 calculable number of ages in which the creation (^j and extinction 

 of a large number of genera, and thousands of species, had taken 

 place, some few only of the first created genera, such as Lingula, 

 Discina, and Crania, have fought their way and struggled for 

 existence through the entire sequence of geological times. Many 

 were destined to a compai-atively ephemeral existence, while others 

 had a greater or lesser prolongation of reproduction. These 

 remarks led hiai to give some extracts from a letter which he 

 received from Darwin as far back as the 26th of April, 1861. In 

 that letter, that eminent and admirable observer writes, " I do not 

 know whether you have read my ' Origin of Species.' In that book 

 I have made the remark, which I apprehend will be universally 

 admitted, that, as a whole, the fauna of any formation is inter- 

 mediate in character between that of the formation above and 

 below. But several really good judges have remarked to me 

 how desii-able it would be that this should be exemplified 

 and worked out in some detail, and with some single group of 

 beings. Now, every one will admit that no one in the world could 

 do this better than you with Brachiopods. The result might turn 

 out very unfavourable .to the views which I hold ; if so, so much the 

 better for those who are opposed to me. But I am inclined to 

 suspect that, on the whole, it would be favourable to the notion of 

 descent with modification. I can hardly doubt that many curious 

 points would occur to anyone thoroughly instructed in the subject, 

 who could consider a group of beings under this point of view of 

 descent with modification. All those forms which have come down 



