CONCHO £R A . 47 1) 



Shell orbicular, compressed, concentrically striated, pale 

 ligament sunk ; lunule deep ; hinge like Cytherea ; margins 

 even ; pallial sinus deep, angular, ascending. 



Animal with a large hatchet- shaped foot, projecting from the 

 ventral margin of the shell ; mantle-margins slightly plaited ; 

 siphons united to their ends ; orifices simple ; palpi narrow. 



Distribution, 100 species. Boreal — Tropical seas ; low water 

 80 fathoms. 



Fossil, 13 species. Carb — . United States, Europe, South 

 India. 



Sub-genera. Cydina, Desh. Y. Sinensis, Chemn. Orbicular, 

 ventricose, margins crenulated, no lunule, sinus deep and 

 angular. Distribution, 10 species, Senegal, India, China, 

 Japan, West America. Fossil, 1 species. Miocene, Bordeaux. 



(Jlementia (papyracea) Gray. Thin, oval, white ; ligament 

 semi- internal ; posterior teeth bifid, sinus deep and angular. 

 Animal with long, united siphons, and a large crescentic foot, 

 similar to Artemis. Distribution, 6 species. Australia, Philip- 

 pines. 



Ltjcinopsis, Forbes. 



Synonyms, Dosinia, Gray, 1847 (not Scop.). Mysia, Gray, 

 1851 (not Leach). Cyclina, Gray, 1853 (not Desh.). 



Type, Yenus undata, Pennant, PI. XX., Fig. 13. [Lucina 

 and opsis like.) 



Shell lenticular, rather thin ; right valve with 2 laminar, 

 diverging teeth, left with 3 teeth, the central bifid ; muscular 

 impressions oval, polished ; pallial sinus very deep, ascending. 



Animal with mantle-margins plain; pedal opening con- 

 tracted ; foot pointed, basal ; siphons longer than the shell, 

 separate, divergent, with fringed orifices. (Clark.) 



The type of this genus having been erroneously placed in 

 Cyclina by M. Deshayes, he has proposed a new genus {Lajon- 

 hairia) for L, decussata, Philippines, a fossil of the English 

 Pliocene, but still living in the Mediterranean. 



Distribution, 10 species. North America, Norway, Britain. 



Fossil, 3 species. Pliocene. Britain, Belgium. 



Tapes, Miihlfeldt. 



aS'2/w ony ?ns, Paphia, Bolten, 1798. Pullastra, G. Sby. Omaliai 



Ryck, 1856. 



Example, T. pullastra, PL XX., Fig. 14. [Tapes, tapestry. 1 

 Shell oblong, umbones anterior, margins smooth ; teeth 3 in 



oacih valve, more or less bifid ; pallial sinus deep, rounded. 



