TEREDO. 81 



means improbable that it may have established itself equal- 

 ly with the two preceding in the timber of our jetties, &c.; 

 unfortunately, too many who have the opportunities of 

 taking these animals upon the renewal of the piles, satisfy 

 their curiosity by preserving merely the perforated wood, 

 or the testaceous tubes, leaving us still in doubt by what 

 species the cavities have been effected. It is with some 

 little hesitation, then, that we include this and the succeed- 

 ing in our Fauna, which we are induced to do, rather from 

 the example of preceding writers, and the fact that they 

 are not noticed in any known continental work as natives 

 of another country, than from any positive proof of strict 

 naturalisation. 



The shape of the valves is very different from that of 

 Norvagica or Batava, the medial portion being decidedly 

 more elongated, and the lower end of the auricle slightly 

 more remote from the ventral tubercle than is that of 

 the front triangle. This latter occupies less than two-fifths 

 of an imaginary line drawn from the beaks to the base of 

 the shell, and is concentrically traversed by raised striae, or 

 narrow lyra>, which are moderately close-set, and not much 

 arcuated below, but more distant and more curved towards 

 the commencement of the series. These are succeeded by 

 another set of minutely decussated strise, which occupy the 

 narrow strip situated between the lateral triangle and the 

 internal radiating groove, and are produced thence along 

 the front margin of the shell. Then follows a still narrower 

 strip, which, together with the preceding, is elevated 

 towards the beaks above the remainder of the surface, 

 covered with very oblique, distant, raised, concentric 

 striulae, often with finer intermediate ones, which, after 

 passing the central, shallow, groove-like, radiating area, are 

 more or less distinctly continued over the remainder of the 



VOL. I. M 



