Partners in ResearcJi. 145 



deposits of the earth are divided by specialists into 

 three principal groups the primary, in which the old 

 red sandstone and the coal-bearing series are among 

 others comprised ; the secondary, of which the gault 

 and the chalk are well known ; and the tertiary, this 

 last being again subdivided into eocene, meiocene, 

 and pleiocene. All the stratified deposits later than 

 these are called, according to fancy, pleistocene, or 

 post-pleiocene, or quaternary, or post-tertiary. In 

 these the fossils have often a great affinity to organ- 

 isms still existing, and often belong to identically the 

 .same species as animals now living. Though the 

 proposed paper was to refer chiefly to the Scotch 

 deposits, illustrative species from England and Ireland 

 were not to be excluded from it. 



In course of time Dr. G. S. Brady joined Messrs. 

 Crosskey and Robertson, especially with a view to 

 the investigation of the ostracoda, which are Crustacea, 

 generally of microscopic size, having their soft parts 

 shielded by a pair of valves, which give them the 

 appearance of tiny bivalved shells. 



As the shells of mollusca were a principal group in 

 the deposits, they had to be carefully authenticated, 

 and, in dealing with these, they obtained the assist- 

 ance of Gwyn Jeffreys. But before any help could 

 be available in determining the fossils, the fossils 

 themselves had to be hunted up and sorted out. 



To those who have never made natural history 

 collections and inquiries, or who have limited their 

 efforts to picking up some worn, empty shells on the 

 shore, and keeping them jumbled together in a box, 

 .all that has been said will convey but a very vague 



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