TELLINA. 375 



of Leach's genus Arcopagia, which Leach himself has 

 since denominated Cydippe. It is the Pectunculus de- 

 pressior of Da Costa, T. rigida of Pulteney, T. subro- 

 tunda of Deshayes, and Cydippe Listeriana of Leach; the 

 young appears to be the Arcopagia ovata of Brown, and 

 (in a " depauperated " and dirty state) is certainly the 

 T. maculata of Turton. Adams's species of the last 

 name is probably the T. bimaculata of Linne, a very 

 common West-Indian shell. 



B. Shell triangular, inequilateral, produced at the posterior 

 end to an angular point, concentrically striated (one spe- 

 cies having the right valve sculptured also by oblique 

 longitudinal stria?); lateral teeth wanting or imperfectly 

 developed. 



3. T. bal'thica *, Linne. 



T. balthica, Linn. Syst. Nat. p. 1120. T. solidula, F. & H. i. p. 304, 

 pi. xx. f. 6. 



Body thick, pale yellowish, tinged with different shades of 

 brown : mantle of a firm texture, fringed with fine, but short, 

 white filaments : tubes nearly hyaline, varying considerably in 

 length both collectively and individually ; the excretal one is 

 curved upwards, and usually longer than the other, being often 

 exserted to almost twice the length of the shell, plain at its 

 orifice ; the alimentary tube has from four to six very minute 

 dentations at its aperture : gills two only, one on each side, 

 rather elongated : palps enormous, triangular, broad at their 

 bases and pointed at their extremities, smooth without and 

 distinctly striated within : foot white, very large, muscular, of 

 moderate length, slightly bent. 



Shell more triangular than round, usually convex and 

 sometimes almost globular, varying in thickness according to 

 the nature of its habitation, opaque, glossy : sculpture, fine, 

 minute, and close-set but irregular concentric stria), diversified 

 by occasional lines of growth : colour, of all hues and shades 

 from milk-white or yellow to crimson, often relieved by narrow 

 zones or concentric belts of a deeper tint, rarely pink in the 



* Inhabiting the Baltic. 



