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appearance of tubular points proceeds from the remains of an inves- 
titure with that curious madreporean substance, which was figured, as 
forming a similar covering, in Plate XII. Fig. 1 and 2, of the second 
volume of this work. That this was the substance which gave the echi- 
nated surface in Lamarck’s F. echinata, the accuracy of that naturalist 
prevents our supposing. A very remarkable circumstance, however, 
here presents itself for our attention — a similar fossil body, the tube 
of different species of fistulanee, is found in different parts of Wiltshire 
and Somersetshire, in Germany, and in France, covered by the pecu- 
liar madreporean labours of an insect, traces of whose existence, 
elsewhere, are very rarely to be found. 
CXXIX. Teredo. A bivalve shell, contained in the lower end of a 
cylindrical tubular shell, generally open at both ends, two opercula 
being adapted to the upper end. 
Having already, in the first volume, dwelt upon the appearances 
yielded by the wood which has been subjected to the ravages of the 
inhabitant of this shell, and which has afterwards undergone the 
change of petrifaction, I shall only now place before you the very in- 
teresting observations of Mr. Home, on the anatomy of the Teredo 
navalis, and on that of the Teredo gigantea, of Sumatra, another 
species which has lately been discovered. 
After a violent earthquake at Sumatra, in the year 1/97, these shells 
were discovered in a small sheltered bay, with a muddy bottom, sur- 
rounded by coral reefs, on the Island of Battoo, distant from the coast 
of Sumatra about twenty leagues. 
The length of the longest of the shells obtained by Mr. Griffiths, who 
brought them to England, was 5 feet 4 inches, and the circumference 
at the base 9 inches, tapering to 1 1 inch at the point. The large end ot 
the shell is completely closed, and has a rounded appearance : at this 
part it is very thin. The small end, or apex, is very brittle, and is 
divided by a longitudinal septum running down for eight or nine inches, 
forming it into two distinct tubes, enclosed within the outer one, from 
