82 



POST-TERTIARY ENTOMOSTRACA. 



although none are now found living in that locality, the destruction having been 

 evidently occasioned by a bank of sand having been thrown over the haunts of that 

 Mollusc during a violent storm. After every great storm, indeed, there is probably 

 some change in the habitats of the Mollusca. 



The Pecten maximus bed at Colintraive, however, contains species which would require, 

 when living, a greater depth of water than they could have enjoyed in their present 

 situation. 



It can be traced along the shore until it can be seen resting upon an old glacial 

 clay containing in abundance Tellina calcarea ; and this, again, may be seen resting 

 on the laminated clay, and the laminated clay on the Boulder Clay, in regular descending 

 order. 



It is evident that at the junction of the edge of the Pecten maximus bed with 

 the Arctic clay, it will be possible for the contents of the two beds to be confused 

 together. 



We have observed this same Pecten maximus bed cropping out in various districts. 

 It may be seen at dead low-water near Tigh-na-bruaich and at Kilchattan Bay, Bute. 



At Eairlie (Ayrshire) it is largely developed, and, as at Colintraive, overlies the 

 Arctic shell-clay. The ground at Eairlie has been so often dug and re-dug by 

 collectors that the natural difficulties in the way of discriminating between the two beds 

 have been increased, and very little, if any, reliance can be placed upon the accuracy of 

 catalogues of so-called ' glacial fossils ' based upon specimens from that locality. Not 

 only specimens from the P. maximus bed, but recent specimens have been thrown 

 together in the debris of the very numerous excavations which have been made, and 

 have thence made their way into collections and catalogues as belonging to the 

 " Clyde Beds." 



The Ostracoda found are a mixture from the various beds now described, species 

 from one deposit having been washed into another, so that it is not necessary to give a 

 separate catalogue of them. 



3. Irvine Water, Ayrshire. 



On the Ayrshire coast, in the neighbourhood of Irvine, a fine sand similar to that now 

 edging the sea has been deposited and drifted inland to a considerable distance, rising in 

 a succession of slightly elevated knolls. Near the shore these knolls are most distinctly 

 marked, having been recently formed, and their loose material not having been driven 

 over the dividmg gaps made by the wind. Inland their divisions have been to a great 

 extent obliterated by perpetual driftings, but excavations show the sand rising and falling 



