456 MANUAL OF THE MOLLtSCA. • 



from tlie Philippines, as seen on removing the left valve, and 

 part of the mantle within the pallial line ; b-c, the large pedal 



opening ; the arrows indicate 

 the small plain incurrent orifice, 

 and the valvular excurrent ori- 

 fice ; /, the foot, contracted in 

 sjoirit ; p p, the large striated 

 palpi ; I, the liver ; the outer 

 gill has a simple margin, the 

 inner is grooved and conducts 

 to the mouth. This genus has 

 higher claims than Kellia to be 

 regarded as the type of a 

 family. 



Fig. 255. Diplodonta. 



LiJCiNA, Bruguiere. 



Etymology, Lucina, a name of Juno. 



Type, L. Pennsylvanica, PI. XIX., Fig. 6. 



Shell orbicular, white ; umbones depressed ; lunule distinct ; 

 margins smooth or minutely crenulated ; ligament oblique, 

 semi-internal ; hinge-teeth 2.2, laterals 1—1 and 2—2, or obso- 

 lete ; muscular impressions rugose, anterior elongated within 

 the pallial line, posterior oblong ; umbonal area with an oblique 

 furrow. 



Animal with the mantle freely open below; siphonal orifices 

 simple ; mouth minute, lips thin ; gills single on each side, very 

 large and thick ; foot cylindrical, pointed, slightly heeled at the 

 base. 



The foot of Lucina is often twice as long as the animal, but is 

 usually folded back on itself and concealed between the gills ; 

 it is hollow throughout. L. ladea [Jjoriipes, Poli.) has a long 

 contractile anal tube. L. tigrina (Codakia, Scop.) has the liga- 

 ment concealed between the valves, its lateral teeth are obsolete. 



Distribution, 70 species. "West Indies, Norway, Black Sea, 

 New Zealand; 120 fathoms. 



Fossil, 250 species. U. Silurian — . United States — T. del 

 Fuego ; Europe — Southern India. 



Sub-genera, &ryptodon, Turton. L. flexuosa, PI. XIX., 

 Fig. 7. Synonyms, Ptychina, Phil. Thyatira, Leach. Clausina 

 (ferruginosa) Jefifr. Shell thin, edentulous ; ligament quite in- 

 ternal, oblique. Animal with a long anal tube. Distribution, 

 o species. Norway — New Zealand. Fossil, 2 species, Eocene — . 

 United States, Europe. 



Fsathura, Deshayes. Anterior adductor scar long, narrow ; 

 hinge- teeth 2.2; umbones imperceptible. 



