INVERTEBRATE PALAEONTOLOGY. 261 



contorted burrows, and narrow elongate valves of the latter. He admits 

 Calobates of Gould, however, as a subgenus under Teredo. Adopting this 

 view, the typical section and subgenus may be separately characterized as 

 follows : 



1. teredo, Linnaeus (typical). 



Animal with siphonal palletes, simple, oblong, often truncated. — 

 (Type as above.) 



2. CALOBATES, Gould. 



Animal with siphonal palletes, large, stilt-shaped, and bony. — 

 T. t/ioracites, Gould. 



It is scarcely necessary to remark that it would generally be impossible 

 to distinguish among fossil species the last section, or, indeed, the groups 

 Xylotrya and Uperotus, from the typical Teredines, by the differences observ- 

 able in the palletes alone, because these delicate parts are very rarely found 

 in a fossil state. The differences in the shells and tubes of Xylotrya and 

 Uperotus, however, will, perhaps in most cases, enable the palaeontologist to 

 distinguish them from Teredo. 



The ship-borers, or " ship- worms," as the Teredines are often (from the 

 worm-like form of the animal) improperly called, were well-known, even to 

 the ancients, in consequence of their habit of burrowing in the bottoms of 

 ships, and all other wooden structures exposed to the sea-water, or sometimes 

 even to brackish-waters. The injury they do in this way is often very great ; 

 and there seems to be no reliable means of preventing their ravages, except- 

 ing the expensive one of applying copper or other metallic sheathing over 

 the whole of the submerged surface.* Like some other pests, however, their 

 injurious habits are not wholly unattended by some compensating good, as 

 they often cause old wrecks and floating timbers, that would otherwise 

 obstruct the entrances to harbors and rivers, to break to pieces and disappear. 

 Their burrows, or borings, usually follow more or less nearly the direction of 

 the grain of the wood, excepting at the immediate start into the side of 

 planks or timbers, but are often tortuous, and generally lined with a calca- 

 reous secretion. They increase gradually in size from the external opening, 

 which is very small and never increases in size, to the inner extremity ; and, 

 in excavating their way in, the animals scrupulously avoid coming in contact 



* I was informed iu Florida, that the " ship-borer" will not attack piles or other structures made 

 of the trunks of Palms; but these are not solid and tirm enough for structures requiring great strength. 



