CONCHIFERA. 
167 
Genus 68.—PHOLAS.— Linnaeus . 
Generic Character. —Animal without a tubular sheath, pro¬ 
jecting anteriorly into two united tubes, frequently surrounded 
by a common skin, and the posterior extremity provided with a 
short muscular foot, flattened at its extremity. — Shell bivalve, 
equivalve, transverse, gaping at both extremities, with various 
accessory pieces either on the hinge or below it ; inferior margin 
of the valves inflected. 
Pholas crispatus.— The Curled Pholas. 
Plate XCI. fig. 17. 
Somewhat oval; reticulated on the anterior half, and separat¬ 
ed from the plain wrinkled half by a broad furrow down the 
middle. Two inches long and three broad. Inhabits the Bri¬ 
tish coasts. 
TRIBE IV.-TUBICOLA. 
Shell contained in a testaceous sheath distinct from its valves, 
incrusted wholly or partly in the wall of this tube, or projecting 
outwards. 
Genus 69.— TEREDO.— Linnaeus. 
Generic Character. —Animal elongated, worm-shaped, invest¬ 
ed in a testaceous tube, boring into wood ; with two anterior, 
projectile, short tubes, and two opercular processes, adhering to 
the sides of the tubes; with a posterior short muscle, pro¬ 
tected by a bivalve shell.—-Tube testaceous, cylindrical, and tor¬ 
tuous, pervious at both extremities, and covering the animal— 
Shell bivalve, placed externally, and outside the tube. 
Teredo navalis .— The Ship Teredo, or Ship-Worm. 
Plate XCI. figs. 18 to 22. 
Cylindrical, taper, smooth, white, somewhat flexuous, finely 
striated longitudinally. Inhabits the European seas, in timber. 
Genus 70.—TEREDINA.— Lamarck. 
Generic Character. —Tube testaceous, tubular, cylindrical, 
closed at the posterior extremity, but exhibiting the two valves 
of the shell ; anterior extremity open. 
