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 there 
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 lving 
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 Quarternary 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 
