MARINE MOLLUSCA OF THE UNITED STATES. 129 
prominent, nearly terminal; hiatus narrowly elongate, nearly ex- 
tending the total length of the shell; dorsal and ventral margins 
nearly parallel. 
Length 16, alt. 6 mill. 
Beaufort, N. C. CW. Stimpson.) 
Family TEREDID&, Carpenter. 
Lectures on Mollusca, 100. 1861. 
The shelly tube of the ship-worm. is subcylindrical, divided 
longitudinally and often concamerated by numerous, incomplete, 
transverse partitions ; the siphonal palettes or stylets assist in 
compressing and relaxing the siphons to facilitate the flow of 
water through the long canal. 
The Teredines live in most seas, perforating wood in the direc- 
tion of the grain by means of the mechanical attrition of their 
valves; these tortuous perforations are lined by calcareous matter 
forming the tubes. The animal is useful in destroying fragments 
of wrecks and floating timber, but causes great destruction to 
dikes, wharves, and to ships when the timbers are not protected 
from its ravages. 
Synopsis of Genera. 
Pallets simple. TEREDO. 
Pallets compound, the blade penniform, composed of a number of jointed 
sete. XYLOTRYA. 
Genus TEREDO, Linnzus. 
Syst. Nat., edit. x., p. 651. 1758. 
1. T. pinataTa, Stimpson. Figs. 272, 273, and 274. 
Bost. Proc., iv. 118. 1851. 
Diameters nearly equal; wing large, not ascending so high as 
the beak, but passing off from it by a gentle slope, descending 
below the anterior triangle, having no defining exterior groove, 
slightly concave and then reflected outwards on the internal face; 
pallets very small, battledore-shaped; end of tube concamerated. 
Length and alt. 12.5 mill. 
. 
Massachusetts to So. Carolina. 
This species differs from 7. megotara, Hanley, which it greatly 
resembles, in the smaller altitude of the valves, the greater breadth 
of the auricle, which is also placed much lower, and in its con- 
camerated tubes. 
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