18 POPULAR BRITISH CONCHOLOGY. 



perforated by Xylopliaga dorsalisj and labelled as from the 

 dock-gates, Ardrossan. Not having heard of this animal 

 before attacking the fixed timber of our harbours (it has 

 been found in driftwood, or portions of vessels cast ashore), 

 I made immediate inquiry respecting it. The piece of wood 

 sent was a portion of the dock-gates. The Xijlo]f)haga has 

 been known to be consuming them since the docks were 

 opened, in March, 1844. It has been known for a very 

 considerable time along this coast, wdiere there is no fresh 

 water. It attacks timber of all kinds; for instance, the 

 wooden pier (the supporters of which are nearly destroyed) 

 and other timbers that are under water about the quays, 

 and have been placed there without any preservative coating. 

 It appears to prefer black birch to any other timber, but 

 does not like African or American oak. The only success- 

 ful preventive made use of for preserving the dock-gates 

 against the Teredo, Xylopliaga, etc., is Muntz's patent yellow 

 metal sheathing, which is put on to the height of thirteen 

 feet ; it lasts for ten or twelve years. The timber that is 

 perforated is always covered by water. The depth of water 

 in the docks is from sixteen to eighteen feet. It may give 

 some idea of the frequency of the Xijlopliaga' s perforations 

 in the different pieces of wood, to mention, that on an ave- 



