2go Mr. Home on the Teredo Gigantea 
Fig. 3. The teredo navalis from Sheerness, with the tubes 
protruded and the opercula in their situation. The letters 
denote the same parts as in Fig. 2. In this figure the cup 
containing the opercula and tubes is distinctly seen, and these 
parts are represented in their natural situation. 
Fig. 4, Represents the external surface of one of the oper- 
cula of the teredo gigantea. 
Fig. 5, Shows the other side of the same operculum. 
Fig. 6 , Shows a side view of the boring shell of the same 
teredo with the process that projects from its concave surface, 
and its cutting edge. 
Fig 7 and 8, Show the two sides of one of the opercula of 
the teredo navalis. 
Fig. g and 10, Show two views of the boring shell of the 
same teredo. 
All these figures are of the natural size of the parts they 
represent. 
Plate XIII. 
In this plate are three figures of the teredo from the British 
Museum, to show its internal structure; the different parts 
are represented of their natural size. 
Fig. 1, Represents the animal laid open through the whole 
extent, exposing the abdominal view. 
aa. The boring shells. 
bbbb, The external covering divided and turned back. 
c, The larger tube, which conveys the sea-water into that 
cavity, in its completely retracted state. 
d. The orifice, by which the sea-water passes out, between 
the boring shells and the proboscis into the space before the 
mouth. 
