36 Stewrart — List of Estuarine Clay Fossils. 



Spiroloculina limbata. Rare. 

 Spiroloculina planatula. Very rare. 

 Triloculina Brongnairtii. Rare. 

 Triloculina trigonula. Common. 

 Truncatulina lobatula. Not common. 

 Verneuilina polystropha? Very rare. 



In the foregoing list I have given estimates for the several species, 

 approximating as near as possible to the abundance or paucity of speci- 

 mens. These estimates are founded on careful observations, extending 

 over some three years. In preparing them I have derived valuable assist- 

 ance from Dr. Grainger's previously published lists, and I am confident 

 that they may be relied on as in the main correct. Future excavations, 

 if such be carried on in these beds, may possibly make slight modifications, 

 but I am satisfied that on the whole the estimates here given will remain 

 practically undisturbed. 



In the table which follows, I have endeavoured to give for the North of 

 Ireland the distribution of these species in Post-tertiary times. Unfortu- 

 nately the unproductiveness of our Glacial beds renders one column rather 

 imperfect. Out of 140 species here recorded, only 29, being 21 per cent., 

 appear as glacial shells in this district. It cannot be doubted but that therms 

 existed a much greater community between the two faunas. 



Species make their appearance in a locality, becoming more and more 

 abundant until they reach their culminating point, from which they recede 

 with more or less rapidity until finally they are replaced by others. Such 

 is the history of many of the shells of our Estuarine Clay, and to make 

 this record as useful and complete as possible, columns are here given, 

 showing those now found living in the waters of our bay, and those 1 iving 

 at present on the coasts of the North of Ireland, distinguishing them from 

 such as have only been found as dead shells. These columns will, it is 

 hoped, prove instructive. It will be seen that many species, now only 

 found dead, existed here during some portion of the Estuarine Clay times 

 in abundance ; and it may be added that during that period some other 

 species, now among the forms dominant in our waters, were either absent 

 or rare. 



Shells from Raised Beaches, and Quaternary Gravels, are not included 

 in these lists, which have been rigidly restricted to species which certainly 

 occur in the Estuarine Clay. Many Post-pliocene shells are thereby ex- 

 cluded, which have been recorded as from Belfast deposits. It is to be 



