202 



appearance of tubular points proceeds from the remains of an 1 inves- 

 titure with that curious madreporean substance, which was figured, as 

 forming a similar covering, in Plate XII. Fig. 1 and 2, of the se- 

 cond volume of this work. That this was the substance which gave the 

 echinated surface in Lamarck's F. echinata, the accuracy of that natu- 

 ralist prevents our supposing. A very remarkable circumstance, how- 

 ever, here presents itself for our attention a similar fossil body, the 

 tube of different species of fistulanse, is found in different parts of Wilt- 

 shire and Somersetshire, in Germany, and in France, covered by the 

 peculiar 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 inha- 

 bitant of this shell, and which has afterwards undergone the change of 

 petrifaction, I shall only now place before you the very interesting obser- 

 vations 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 1797, 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| inch at the point. The large end of 

 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 longitudiaal septum running down for eight or nine inches, forming it 

 into two distinct tubes, enclosed within the outer one, from whence the 



