1902. . HiNCH. — Glacial Geology of Co. Dubliyi. 231 



have been obtained. Over this bed, and covering it like a 

 protective hood, is a layer of fine Boulder-clay varying from 

 a foot to three feet in thickness. In this bed Mr. Praeger 

 (whom I have to thank for aid at every stage in the 

 work of collecting, and advice in the writing of this paper) 

 found a fragment oiAsta^'te compressa. On this bed of Boulder- 

 clay, in the left hand corner of the section, is a large accumu- 

 lation of pebbles cemented with carbonate of lime. Over 

 the Boulder-clay and the calcrete is a bed of limestone sand 

 and gravel, with an occasional erratic of granite, mica-schist, 

 etc. This bed is over 30 feet in thickness, and yields a few 

 shelly fragments on careful examination. The adjoining pit 

 reproduces the granite boulder bed, and the upper limestone 

 gravel, but the calcrete is absent, and the Boulder-clay bed 

 is reduced to a thickness of a few inches. The following is a 

 list of the moUusca obtained from the granite boulder bed, in 

 the naming of which I have received valuable assistance from 

 Mr. E. T. Newton :-- 



IvAMEI,I,IBRANCHIATA : 



Ostrea edulis, L,inn.— Mr. W. B. Wright collected a piece of this 

 shell if X i\ inches. I got four other fragments. *N'.S. 



Pectcn varius, Linn. — One fragment. N.S. 



P. opercularls, Linn. — Two fragments. N.S. 



P. maxlmus, Linn. — Four fragments. N.S. 



Mytilus sp. — Fragments. 



Nucula nucleus, Linn. (.^) — One fragment. 



Nuculana (Leda) pernula, O. F. Miiller. — Two complete valves 

 and forty fragments, mostly hinges. N. 



Cardium echlnatutn, Linn. (?)— Five fragments, 



C. tuberculatum, Linn (.^). — Three fragments. 



C. edule, Linn.— Two half valves, thirty fragments. N.S. 



C. norvegicum, Speng.— Four fragments. N.S. 



Cyprina islandica, Linn.— Thirteen hinges and two hundred 

 fragments. B.N. 



Astarte toorealls, Chem.— Twenty hinges. N. 



A. compressa, Mont.— Eight complete valves, twenty frag- 

 ments. B.N. 



A. sulcata, Da Costa.— Twenty fragments. N.S. 



Artemis exoleta, Linn.— Two hinges. N.S. 



Venus caslna, Linn. <^.>)— Three fragments. N.S. 



* N.S. signifies that the distribution ot this species is north and south 

 of Britain; B.N. that the distribution is confined to British and 

 northern seas ; N. that the species is extinct in the British seas, and is 

 arctic in distribution at the present day. 



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