CONCHIFEPA. 507 



into the sipiional tube ; siphons very long, united nearly to the 

 end, attached at the bifurcation and furnished with 2 shelly 

 pallets or styles ; orifices fringed. 



T. Navalis is ordinarily a foot long, sometimes 2| feet ; it 

 destroys soft wood rapidly, and teak and oak do not escape ; it 



Fig. 270. Ship-worm, Teredo Norvegica, removed from its burrow. 



always bores in the direction of the grain unless it meets tha 

 tube of another Teredo, or a knot in the timber.* In 1731-2 it 

 did great damage to the piles in Holland, and caused still more 

 alarm ; metal sheathing and broad-headed iron nails have been 

 found most effectual in protecting piers and ship-timbers. The 

 Teredo was first recognised as a bivalve mollusc by Sellius, who 

 wrote an elaborate treatise on the subject in 1733. (Forbes.) 



T. corniformis, Lamarck, is found burrowing in the husks of 

 cocoa-nuts and other woody fruits floating in the tropical seas ; 

 its tubes are extremely crooked and contorted, for want of 

 space. The fossil wood and palm-fruits {Nipadites) of Sheppy 

 and Brabant are mined in the same way. The tube of the giant 

 Teredo {T. arenaria, Eumph. Furcella, Lamarck) is often a yard 

 long and 2 inches in its greatest diameter ; when broken across 

 it presents a radiating prismatic structure. The sij)honal end 

 is divided lengthwise, and sometimes prolonged into two diverg- 

 ing tubes. T. Norvegica and T, nana are divided longitudinally 

 and also concamerated by numerous, incomplete transverse 

 partitions at the posterior extremity. 



T. palmulata (Xylotrya, Leach) has the siphonal pallets elon- 

 gated and penniform (PL XXIII., Pig. 28); a species with 

 similar styles occurs in the fossil wood of the Greensand of 

 Blackdown. 



Distribution, 21 species. Norway, Britain, Black Sea; Tro- 

 pics : — 119 fathoms. 



Fossil, 24 species. Lias — . United States, Europe. 



Sub-genus. Teredina, Lamarck. T. personata, PI. XXIII., 

 Figs. 24, 25. Eocene, Britain, France. Valves with an acces- 

 sory plate in front of the umbones ; free when young. The 

 tube is sometimes concamerated; its siphonal end is often 

 truncated ; and the opening contracted by a lining which makes 

 it hour-glass shaped, or six-lobed (Fig. 25 a.). 



* The operations of the Teredo suggested to Mr. Brunei his method of tunnel ling 

 the Thames. 



