TELLINA. 129 



animal is like that of T. tennis, which has only a single amal- 

 gamated branchial lamina on each side, and belongs to our 

 second section ; in that case, the T. fabula must march with 

 it. But this point may easily be set at rest, as the species is 

 common, though not in my district. The T. proximo, is exotic 

 or fossil. The T. bimaculata is exotic. 



The T. balaustina of British origin has much similarity to 

 specimens of T. crassa of the same size ; the hinge, teeth, cica- 

 trices, and pink radiating pencils are identical ; the chief dif- 

 ference is the greater tumidity and tenuity of the valves, and 

 the absence of the short vertical lines between the striae of 

 increment. 



Section II. Animal with a single branchia on each side. 



T. TENUIS, Da Costa. 

 T. tennis, Brit. Moll. i. p. 300, pi. 19, f. 8; and (animal) pi. K. f. 3. 



Animal very flat ; mantle sufficiently open in the ventral 

 range, finely fringed, produced posteriorly into two white 

 siphons, separated from their bases, of about equal length and 

 diameter ; both of them are often exserted beyond the length 

 of the shell ; the anal is usually the longest, and curves up- 

 wards; but these circumstances depend on the will of the 

 animal. There is only one very large pale brown, excessively 

 membranous, subtriangular branchia, on each side, with the 

 finest pectinations, fixed under the posterior dorsal range, 

 where its point becomes united with that of the one on the 

 other side, exactly as in T 7 . splidula, but its margin is not 

 fixed to the body so decidedly ; it is more lax, and can be 

 elevated by a camePs-hair brush, and is connected at the 

 anterior angle by a branchial vein, with a pair on each side of 

 large triangular palpi, but not so much out of size as in 

 T. solidula and Scrobicularia piperata ; they are pectinated on 

 both sides, but more so on the inner surfaces ; the colour is 

 a darkish cloud hue, mixed with paler lines, giving them a 

 mottled aspect ; they are broad at the bases, not very long or 

 pointed. The foot is large, broad, compressed, tongue-shaped, 

 not very pointed, and geniculated. The liver is dark green ; 



