240 



POPULAR CONCHOLOGY. 



pallial impression sinuated posteriorly.* Animal unknown. 

 — 5 species ; also fossil. 



These shells are brought from the American seas. 



Thracia. Leach. — Shell oval, oblong, thin, sub-equi- 

 lateral, inequivalve, a little 

 gaping posteriority; hinge con- 

 sisting of a more or less promi- 

 nent spoon-shaped tooth in 

 each valve receiving the liga- 

 ment ; pallial impression deeply 

 marked. Animal with the man- 

 tle closed, except for the passage 

 of a rather small compressed 

 foot; siphons rather long, not 

 united, and having fimbriated openings ; a single branchial 

 lamina on each side, and the mouth tentacles triangular, 

 and comb-like, f — 8 species ; also fossil. 



These shells are thin, fragile, sometimes rough, and 

 generally covered with an epidermis. They are found in 

 the Mediterranean Sea, and on the coast of Senegal ; and 

 several species on the shores of Britain. 



Magdala. Leach. (Lyonsia Turton ; Osteodesma 

 Desh.; Pandorina Scacchi.). — Shell 

 long, thin, iridescent, inequivalve, 

 somewhat gaping at the sides ; hinge 

 toothless, linear, and having on each 

 side a small sloping furrow, into 

 which the ligament passes, which 

 bears in its middle a small four- 

 sided appendage ; muscular impres- 

 sions small, the pallial has a sinus behind. Animal having 

 two short siphons, which are separated, and slightly pro- 



Magdala norvegica. 



* Sow., Conch. Manual. 



f Forbes's British Moll. 



