116 PHOLADID^. 



Hastings (S. H.), &c. In the north it appears to be more 

 abundant, and is taken at Liverpool (M'Andrew), Scar- 

 borough (Bean), in sand near Hartlepool in Durham 

 (Jeffreys, cab.), in the shale rocks of Northumberland and 

 Durham (Alder). 



In Ireland it is dug from pure sand in an estuary near 

 Dublin (from which vicinity have come some of the finest 

 examples known to us), and is obtained, likewise, from 

 Belfast and Dublin Bay (Thompson), the coast of Cork 

 (R. Ball), &c. 



Dead valves are frequently cast ashore on the Isle of Man 

 (E. F). 



In Scotland, among other localities, may be mentioned 

 the Murray Frith (M'Andrews), Frith of Forth, where it 

 is found in abundance burrowing in the coal-shales exposed 

 at low water, in company with P. crlspata (E. F.), Clyde 

 (Smith), Aberdeenshire (M'Gillivray). 



Mr. Clark has obtained this species at Guernsey, " from 

 the sandstone, from which the waterproof cement is made." 



The Pholas crispata is distributed generally throughout 

 the European seas, and is the only one of our Pholades 

 which ranges to the shores of North America. It occurs 

 on the coasts of Massachussets and New Jersey. This 

 wide distribution is connected with its geological history. 

 It is one of the species which ranged throughout the upper 

 part of the northern hemisphere during the pleistocene or 

 glacial epoch, in the ancient sea-beds of which time it is a 

 common fossil. Before that period it had lived within our 

 area during the successive epochs of the coralline and red 

 crags. It is an interesting Instance of a littoral, or subllttoral 

 shell, capable of bearing many varieties of climate, having 

 consequently a great range In time, and In the end a wide 

 and peculiar geographical distribution. 



