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never the ease during life, and could not have arisen from 

 the weight of the superincumbent deposit, the effect of 

 which is seen on numbers of specimens entirely crushed 

 in every position; therefore is solely owing to the decom- 

 position of the muscular attachments aud ligaments. I am 

 aware that various opinions exist as to the fresh- water origin 

 of the mussel band, as proved by the shells, which might 

 possibly have been marine. That they are not marine I 

 conceive is fully proved by the occurrence in the same band 

 of such vast multitudes, almost strata, I was going to say, 

 in some instances of a small species of Entomostraca, which 

 is the only example of the class Crustacea in our Coal Field, 

 and the last animal to which I shall call your attention on 

 this occasion. The creature alluded to is Cypris arcuata. 

 Now, that the genus Cypris is fluviatile or lacustrine is 

 universally admitted ; I cannot see, therefore, how we can 

 account for the myriads of these animals in connexion with 

 the Unionidse, unless they were both tenants of the same 

 fresh-water lake. The habits of these little creatures are 

 well known. They are to be seen in numbers in stagnant 

 waters, marshy pools, ditches, &c., moving about with great 

 rapidity. The Cypris is covered with an oblong sort of 

 shell, of two valves, somewhat kidney-shaped, which is the 

 only durable portion of its body, and which, like many other 

 species of Crustaceans, is shed annually, and will then fall 

 to the bottom of the water, and form a stratum with the 

 Unios ; thus showing us that the former were not suddenly 

 brought to the spot, but inhabited the particular locality for 

 a long period, and left their annual exuviae to attest most 

 clearly the tranquillity of the waters in which they were 

 passing through successive generations. Hence our analysis 

 of animal remains in the Yorkshire Coal Field stands thus — 

 Fish, 1 7 species ; Cephalopods, 5 ; Mollusca and Conchifera, 

 17 ; Crustacea, 1 ; — total 40. 



