407 
remarks on that fossil wood, which is so frequently found on the shore 
of Essex, as well as on the opposite shores, which, being hollowed 
out into tubular cavities, apparently by the labours of the teredo, has 
been distinguished by the name of Lapis Syringoides. 
Representations of specimens of this stone are exhibited at Plate 
VIII. Fig. 8, 9, 10, where the devastating labours of this animal are 
sufficiently apparent. 
It may not be amiss to remind you, that, from the time of Theo- 
phrastus, the lignivorous powers of this creature have been known 
and dreaded. Linnaeus describes it as a terehella, possessing two 
calcareous hemispheres for cutting out, and two for piercing; its 
round bending shell piercing into the wood. Dr. Raster describes 
its head as being of a most wonderful structure, being covered 
with two hard shell -like hemicrania; but of a substance, in reality, 
neither osseous nor testaceous. These hemicrania, which are whiter 
than the rest of their bodies, he speaks of as exceeding in hardness 
the testaceous tube they inhabit : their inner surface, he describes 
as being hollow and smooth; and the outer, convex and rough, 
having three ranges of fibres, passing in different directions. These 
two hemicrania, which are connected by strong ligaments, and, as 
it were, by a small hinge, by which they are able to dilate, without 
separating, besides defending the soft head, are the instruments by 
which the animal procures its food : since being placed in a manner 
similar to a double bit of that kind of boier we call an augur, 
whichever way the head is turned, the raised and rough fibres, either 
of one direction, or of the other, rub off some of the particles of 
the wood*. 
In the year l/SO, the persons appointed to take care of the dykes 
on the coast of Holland and Zealand, observed that the piles made 
of even the hardest oak, and placed for the purpose of defending 
* Philosophical Transactions, Vol. XLI. Part I. No. 453. 
