456 MATOTAI. OF THT: MOLLUSCA. 



fr'^ro tliP Pliilippiues, aa seen on removing the left valve, and 

 part of t.ne mantle ■^'itliia the pallial line ; h-c, the large pedal 



opening; the arrc»Tv.s indicate 

 th3 small plain incvrrervt orifice, 

 and the valvular excurrent ori- 

 fice ; /, the foot, contracted in 

 spirit; 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 



hiffher claims than KelUa to be 

 f> .■ <-> 



regarded as the type of a 



Fii4 356. Diplodonta. f tl 



Ltjcina, Brugui^re. 



Etymology y Lucina, a name of Juno. 



Type. L. Penusylvanica, PI. XIX., Pig. 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 

 farrow. 



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 Litcina 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. Zac^ea (Loripes, Poli.) has a long 

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

 ment concealed betweeo 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. 



Suh-genera, €^ryptod^n, Turton. L. flexuosa, PI. XIX., 

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

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

 ternal, oblique. Animal with a long a,nal tubo. DistributioTif 

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

 United States, Europe. 



Psathura, Deshayes. Anterior adductor scar long, narrow ; 

 hinge-teeth 2.2; umbones imperceptible. 



