covered with excrescences resembling tubercles. There was no in-
dication that the animal had adhered to any part of the shell.
The great length and size of these shells, and the division in the upper part, constitute, in Mr. Griffiths’s opinion, their chief pecu- liarities. The radiated appearance of the substance of the shells is such, that they might, in his opinion, be easily mistaken for stalac- tites. Mr. Griffiths at first considered these shells as a new genus; but afterwards, on consulting the works of Rumphius, he found in that author a description of some shells, very similar, but differing by having two long-jointed tubes issuing from their upper part. These shells were found in shallow water among mangrove-trees.
In the first part of this paper Mr. Home relates some further par- ticulars respecting the sea worm shell from Sumatra, of which an ac- count was, some time since, laid before this Society by Mr. Griffiths. A specimen of one of these shells, five feet long, but imperfect at both ends, was given to Mr. Home by Capt. Maxwell; and in order to remove all doubt respecting its nature, a part of it was analysed by Mr. Hatchett, who found that it was composed of carbonate of lime and an animal gelatinous substance, greater in quantity than in the Chama Gigas, but less than in the common oyster.
The subsequent discovery of two boring shells and two flattened opercula, sufficiently evinced that the shell here treated of belonged to the genus Teredo; and as the internal structure and economy of Teredines are very little known, our author thought that nothing would tend more to enable us to form an adequate idea respecting this new species (which he thinks may be called Teredo gigantea), than an accurate knowledge of the common species Teredo Navah's. With this view, by the assistance of Sir Joseph Banks and Mr. VVhit- bey, Mr. Home obtained some pieces of wood, with live Teredines in them, from Sheerness. By means of these, and of some speci- mens in the British and thezHunterian Museums, he has been enabled, with the assistance of Mr. Clift and Mr. Brodie, to give a very cir- cumstantial description, accompanied by drawings, of the anatomy of the Teredo Navalis.
The Teredines brought from Sheerness, lived in salt water for the space of three days after being brought to town, during which time these animals were observed to throw out two small tubes ; the largest of which was about three fourths of an inch in length, and had, within its external orifice, a fringe composed of about twenty very small tentacula. These tentacula were visible only when the tube was fully extended, because the animal drew in this tube by inverting it; whereas the smaller tube was not inverted when drawn in. The smallest of these tubes appeared to be the most sensible; for the
