TEREDO. SH]P-JJ r ORM. 185 



ter, of a silvery white color, and embossed with numerous 

 pearly white tubercles: the lower half of these quills is 

 clothed with numerous tufts of yellowish lanceolate fringe- 

 like filaments, pointing forwards and disposed in a verticil- 

 late or whirled manner, the lateral ones being elongated 

 and themselves fringed on the inside, giving this part a 

 beautiful pennated appearance. These feathered append- 

 ages can be ejected and retracted at pleasure, and are pro- 

 bably instruments of absorption, as the animal is furnished 

 with a single terminal tube, whose office may perhaps be 

 the discharge and deposit of its eggs or spat. 



In the summer of 1817, a large piece of fir timber was 

 drifted into the mouth of the river Ex, in Devonshire, co- 

 vered on the outside with the Lepas anatifera, and perfo- 

 rated with these interesting animals in a living state. They 

 appear to resemble the species which Lamarck observed in 

 the museum of Cuvier, at Paris, except that he describes 

 the pennated appendages as being jointed : size of the 

 last. v. v, 



3. Teredo dorsalis. Back-valved Ship-ivorm. 



Shell yellowish-white, with often a purplish cast about 

 the hinge, covered with a blackish skin, with a triangular 

 projection as in the two last, but the narrow space beneath 

 is more strongly and remotely striate in an oblique direc- 

 tion, under which is a longitudinal groove bounded by a 

 raised rib : the side opposite the triangular projection is 

 rounded and tumid ; in consequence the front margin is 

 not pointed but well rounded, without the ear-shaped ap- 

 pendage : on the back are two additional oblong transverse 

 curved accessorial valves, one attached to each of the pri- 

 mary valves, and meeting together at the hinge : inside 

 white, glossy, with a strong longitudinal raised rounded 

 rib, extending from the insertion of the primary tooth to 

 the margin, the end of which is thickened by a transverse 

 rib, but not ending in a knob : hinge with the primary teeth 

 as iu the others ? and a single supplemental tooth in each 

 valve seated on the hinge, one of which is tubercular, the 

 other a small reflected point : the tube is rather rugged, 

 dark brown, abrupt and rounded at the lower end, where 

 there are two large circular orifices. 



R 3 The 



