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tig 110 us seas. To this number may be added 4 species, 

 some of which probably exist elsewhere. Nucula similis 

 and Corbula pisum are species of the European Eocene. 

 I can detect no difference between the Matura examples 

 and the English species, but some doubt of coarse rests 

 on the determination, owing to the distance both of 

 locality and of time. I think, from what has been 

 stated, that we may consider it moderately safe to infer, 

 that of the fossil mollusca of the Matura deposit there 

 is a percentage of at least 10 extinct species. This 

 would bring the deposit within the Pliocene period ac- 

 cording to the classification of Eyell*, and in searching 

 for European equivalents, we should probably find that 

 the glacial deposits of Europe present the closest ana- 

 logies with the Matura beds. 



I may remark, by the way, that the fact has not 

 practically been overlooked by Geologists that even 

 where all the species are recent, )^et if some of them 

 are only found in distant seas and existing under dif- 

 ferent climatal conditions to those obtaining in the 

 localities where such species are found fossil, the dif- 

 ferences between the recent and fossil fauna? mark a 

 real progress in geological time, and entitle the strata 

 from which the fossils are obtained to a distinctive name. 

 The Matura deposits are however less remarkable in 

 this respect than in regard to the small size of the shells 

 found in them, a point which will be dwelt upon in the 

 following sections of this paper. 



3. — Conditions of Deposit. 



I shall now proceed to consider the conditions under 

 which the present deposit was formed. It is probable 

 from the sandy nature of the beds, that they were 

 not thrown down at any very great distance from land ; 

 while it is evident that it could not have been in the 

 form of a beach that the deposit was accumulated. 

 The shells are many of them too fragile to have with- 

 stood the attrition which accompanies exposure on a 



* Lyell, Manual of Elementary Geology, 5 ed. p. 105, and 

 Supplement, p. 13. 



