22 LAND AND FRESH-WATER MOLLUSKS. 
rived from the name of M. Driessenus, an apothe- 
cary of Mazeyk, from whom the former received 
in the year 1822 a collection of these mussels 
alive, from a canal near Maestricht. But as 
early as 1824 Mr. J. de C. Sowerby called 
attention to its occurrence in the Commercial 
Docks on the Thames, where it was already 
abundant, and used by anglers as a bait for 
perch, whither it had been brought attached to 
timber from Eastern Hurope. 
The mode by which it has been introduced is 
evidently by its being affixed to the logs of tim- 
ber before they were stowed in the ship’s hold, 
for it has been seen adhering to them before they 
were unloaded, and not that it had attached itself — 
to the ship’s bottom, and so been conveyed. The 
former mode of transport is the more rational, as 
the bivalve can survive a removal from the water 
for several weeks, especially under such favour- 
able conditions as prevail in the moist hold of a 
ship. 
In 18383 it was found in vast abundance in the 
Clyde and Forth Canal, Glasgow; in 1834 it 
appeared in the Union Canal, Edinburgh ; and in 
1836 it was found in considerable numbers on 
the piers of the bridge which crosses the Nen 
at Fotheringay, in which locality it had been in- 
troduced from Wisbeach, on timber, since 1828. 
In 1837, the late Mr. Hugh Strickland found it 
a 
