412 REPORT—1890. 
mixed with seams of fine gravel, larger rocks, and exposures of limestone 
drift. Whether all these drifts here and those of Down and Antrim are 
of the same age as that at Skerries Point and Killiney Bay is question- 
able ; their components are nearly alike, but it may be noticed that in the 
limestone drift proper the rocks are mostly angular, and much glaciated. 
Inthe north of Ireland especially these rocks are very much rolled, and 
have lost most of the striz and other indications of ice action, and from 
this it may be inferred that one is the product of land ice, and the other 
of water. This inference is strengthened by the presence of broken 
shells of Cyprina, in the midst of the rocks in Balbriggan Bay, the true 
limestone drifts being absolutely unfossiliferous, as mentioned already. 
Amongst the grayels small patches of shelly matter are not uncommon 
at the lower part of the cliffs, much comminuted, and hardly identifi- 
able. The fauna is peculiar, yielding the boreal forms. 
Astarte borealis. Cardium echinatum. 
Leda abyssicola. Isocardia cor. 
» arebica, Leda minuta. 
» pernula. Lutraria elliptica. 
Saxicava norvegica. Nucula nucleus. 
Tellina calcarea. Tellina balthica. 
Columbella rosacea. Dentalium entalis. 
Littorina littorea. 
RECENT BRITISH. - obtusata. 
Astarte compressa. Turritella terebra. 
a sulcata. 
Unlike the boreal species found in the clays about Belfast and 
Carrickfergus, the pelecypoda are all in single valves, and evidently not 
in their original habitat. 
The clay is best seen on the shore about a mile and a half north of 
Skerries. The richest part, from whence Canon Grainger got many of 
the rarest species in the above list, is now covered up by masonry. 
Beyond the lighthouse the foreshore slates, schists, and other Ordo- 
vician rocks are capped more or less by the usual clay, with striated 
boulders and local débris. Traces of a raised beach are visible in the 
banks near the town, and in a low cliff at the bend a littie farther on. 
Other portions of this raised beach are present at the other side of the 
bay, by Lowther Lodge. The fauna is strictly local, and in the same 
condition as the more recent shells found upon the shore. 
Where the cliff is at its lowest, marking an old line of drainage, it is 
covered by apparently the remnants of an old sand dane, full of landshells 
of few species, and an abundance of littoral shells. Certain changes have 
occurred in the distribution of these, the periwinkles of the shore differing 
in proportion to those in the sands. Thus, of twenty examples, picked 
at random off the rocks and seaweed, seventeen were Littorina rudis, two 
L. littorea, and one L. obtusata. In the sands, on the contrary, the last 
two species abound, and L. rudis is almost, if not quite, absent. 
Raised Beach Fossils in Balbriggan Bay. 
Aporrhais pes pelecani, Littorina littorea. 
Buccinum undatum. a obtusata. 
Cyprzea europzea. a4 rudis. 
Dentalium entalis. Murex erinaceus. 
Fusus antiquus. Nassa pygmea. 
Helcion pellucidum. », reticulata. 
