TEREDO. 85 



able likeness to a mallet, from which resemblance the name 

 malleolus is derived. It consists of a thin plate or lamina, 

 varying much in shape, but always laterally enlarging to- 

 wards its base, and more or less angular above. From the 

 upper portion of it springs a short, compressed, filiform 

 stalk, which rises centrally about an equal distance from 

 the angle, to that of the latter from the basal termination 

 of the lamina. This stalk is not in the same plane with 

 the plate, but forms a more or less obtuse angle with it, an 

 important character for distinguishing it from all the stages 

 of growth in the caudal appendage oi Norvagica. The two 

 sides which form the angle of the lamina, are usually in the 

 younger and more symmetrical examples (for the pallets of 

 the Teredines vary with their growth), much incurved near 

 the stalk, and bowed out as they recede from it ; the basal 

 line appears sinuous and not rectilinear, in some specimens 

 beinff incurved in the middle, and convex or arcuated at 

 one or both extremities; in others, swollen in the centre, 

 and concave at the extremities. The sides of the lamina 

 bend towards the more concave area. The tube is stated 

 by Dr. Turton to be composed of a slight testaceous de- 

 posit on the inside of the chamber it has excavated, the 

 terminal portion of which is slightly semi-concamerated. 



We cannot regard this species as strictly indigenous, 

 since hitherto it has been almost exclusively extracted from 

 foreign wrecks or floating timber from uncertain localities. 

 The native habitat is Sumatra, (so prolific in Teredines,) 

 and it is by no means probable that a species from so warm 

 a climate should ever become naturalised in our less genial 

 waters. The original describer of malleolus^ obtained it 

 from a piece of spar supposed to have formed part of 

 the Venerable man-of-war which was drifted into Torquay 

 during the prevalence of some heavy gales, that vessel having 



