4. Septaria. One species.
The tube of this genus unquestionably contains a bivalve shell; but, as no perfect specimen has yet been found, nothing decisive is known respecting it.
Tube calcareous, thick, conically elongated, more or less flexuous, as if composed of pieces placed on the ends of each other, or as if articulated, with a ring or projection more or less marked at the place of the joints, but without traces of partitions; terminated on one side by an inflation, oftentimes with some interior partitions, and on the other by two tubes, distinct and sub-articulated.
S. arenaria. The Sand Septaria.
The type of this genus.
5. Teredina. Two fossil species.
A genus without a living species, given here to preserve the family entire, having a shell thick, oval, short, very gaping posteriorly, equivalve, inequilateral; summits well marked; a spoonlike cavity in each valve.
Tube or sheath testaceous, cylindrical; anterior end open; posterior end closed, but exhibiting the two valves of the shell.
6. Teredo. The Ship Worm. Three species.
This genus derived its name from the faculty it possesses of boring wood. The T. navalis can penetrate the stoutest oaken planks of a ship’s sides by means of two valves affixed to the head of the animal. The effects produced would be much more destructive but from the fact of their generally perforating the wood in the direction of the grain. Sir E. Home wrote a very scientific and interesting description of a species not mentioned by Lamarck, called the T. gigantea, found imbedded in indurated mud in the Island of Sumatra. It is the largest species known, some having been seen four or five feet long.