168 TEREDINIDiE. 



Teredo Norve'gica*, Spengler. 



r, norvagicKs, Spengl. Skr. Nat. Selsk. ii. (1) p. 102, t. ii. f. 4-G B, & 

 T. norvagica, F. & H. i. p. 66, pi. iv. f. 1-5. 



Body whitish, or of a light-greyish tint, semitransparent : 

 tubes separated for about one half of their extent; orifices 

 encircled with fine cirri, which are longer and more numerous 

 in the incurrent or alimentary tube than in the other, and are 

 often of various colours, or edged with brown, red, rose, or 

 yellow. 



Shell convex, sohd and opaque, scarcely glossy ; it is 

 parted in the middle by a slight longitudinal crest, with a 

 broad but shallow furrow on the posterior side: sculjpture 

 divided into three distinct portions, viz. anterior, middle, and 

 posterior: the anterior consists of sharp, narrow, and fine 

 transverse plates, from 60 to 80 in number, which are more 

 remote at first, and become closer in subsequent stages of 

 growth ; the edges of these plates are microscopically notched 

 across in an oblique direction ; this portion represents a triangle 

 having an acute apex at the beak of the valve, and a broad 

 and somewhat curved base : the middle portion extends the 

 whole length of the shell, and is strap-like ; the upper part 

 lies between the inner line of the anterior area and the crest 

 which separates one side from the other ; the lower part is 

 open outside, and bounded by the crest on the inner side ; the 

 broadest part is at the point of the angle where the anterior 

 and middle portions join ; this middle portion consists of 

 numerous extremely delicate and nearly equal strife, the edges 

 of which are exquisitely beaded ; these striae are longitudinal, 

 with an oblique tendency towards the posterior end, and they 

 diverge from the transverse plates at a right angle : the pos- 

 terior portion is always smooth, or only marked with concentric 

 and slightly raised lines of growth : colour whitish, with often 

 a tinge or stain of brown on the anterior side, especially the 

 separating line : epidermis membranous, yellowish-brown, 

 sometimes of a very dark hue : marrfins obtusely angular on 

 the upper part of the anterior side, with a large triangular 

 excision on the lower part, so that w^hen the valves are united 

 in their natural position, the opening or gape is broadly heart- 

 shaped ; bluntly pointed or rounded in front ; and incurved on 



* Inhabiting Norway. 



