1088 TEREDO. 



closed by the outer cylinder, and the latter, of which the 

 summit is said by Mr. Griffiths to be very brittle, might 

 probably, either to shew the internal structure, or by accident, 

 have been more broken away than usual ; the Linnasan spe- 

 cific name is moreover ratlier peculiarly applicable from the 

 circumstance of the base being divided into separate cham- 

 bers, as has been observed by Sir E. Home, who after re- 

 lating the manner in which the lower end of a full-grown 

 shell is closed, adds, that in some of Mr. Griffiths's specimens 

 " the animal has receded from its first enclosure, and has 

 formed a second three inches up the tube, and afterwards a 

 third two inches further on." The discovery of the two 

 boring shells and two flattened opercula prove the necessity 

 for its removal to Teredo, and the divided summit gives it a 

 place in Lamarck's Genus Fistulana. Pallas, in his Mis- 

 cellanea Zoologica, p. 140, asserts that llumphius's shell 

 differs only from Teredo tmvalis in being an inhabitant of 

 sand instead of wood ; but Favanne, in describing Le Cierge, 

 maintains a contrary opinion, and among other marks of dis- 

 tinction points out the bifurcated summit. Mr. Griffiths 

 could not obtain a perfect specimen, and the following re- 

 marks are extracted from a memoir with which he favoured 

 the Royal Society, and which in their Transactions imme- 

 diately precedes the observations of Sir E. Home : " The 

 length of the longest of these shells that came into my pos- 

 session was five feet four inches, and the circumference at 

 the base nine inches, tapering upwards to two inches and a 

 half; the colour on the outside milk-white, the inner surface 

 rather of a yellow tinge. This specimen was nearly per- 

 fect, having a small part of the lower extremity entire. I 

 have others of various dimensions, a very good one about 

 three feet long, and four inches round, tapering to an inch 

 and a half at the point." The outer surface is uneven, and 

 strongly wrinkled transversely, hi^t the inner surface is per- 

 fectly smooth ; the internal tubes at the summit are about 

 eight or nine inches long ; in a fragment rather more than 

 an inch and a half in diameter, which Sir Joseph Banks 

 gave me, the thickness of the tube is a quarter of an inch, 

 and the structure is so singularly radiated, that I at first mis- 

 took it for a mineral stalactite. The Serpu/a arenaria of 

 the ]2th edition of the Systema Naturas is an entirely dif- 

 ferent species ; but the following description in the Mus. 

 Lud. Ulr. is more likely to have been intended for the pre- 

 sent shell : " Testa crassa, forma intestini, curvata, irregu- 

 laris, cinerea, inamoena, extrorsum sensim latior apice an- 

 gustiore, saepe in duos ramos bifida." 



