210 LUCINID^. 



Subfamily L UCININ^. 



Shell more or less orbicular, the anterior muscular impression 

 narrower and much longer than the posterior, the ligament is 

 lodged in a deep groove or is sometimes nearly internal. 



LuciNA, Bruguiere, 1792. 



JEtym. — Lucina, a name of Juno. 



Distr. — 100 sp. Universal. Fossil, 250 sp. U. Silurian — ; 

 United States, T. del Fuego, Europe, Southern India. L. Jamai- 

 censis, Linn, (cxix, 40). 



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 obsolete; 

 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. 



CYCLAS, Klein, 1753. (Divaricella, von Martens, 1880.) Valves 

 divaricately striate L. divaricata. Lam. (cxix, 41). West 

 Indies. L. Rigaultiana, Desh., a fossil of the Paris Basin, may 

 also be added to this group. 



CODAKIA, Scopoli, 1777. (Lentillaria„Schum., 1817. ' Jaconia, 

 Recluz, 1869.) Shell flattened, surface radiately flatly ribbed or 

 grooved. L. tigeinna, Linn, (cxix, 42). 



MILTHA, H. and A. Adams, 1856. Shell inequivalve, with 

 nearly smooth surface ; lateral teeth obsolete. L. Childreni, 

 Gray (cxix, 43). 



MYRTEA, Turton, 1822. (Cyrachsea, Leach.) Shell a little 

 compressed, ribbed, crossed by scabrous concentric lines.. Car- 

 dinal teeth one in one valve, two in the other. L. scabra, Lam. 

 (cxix, 44, 45). 



HERE, Gabb. Shell suborbicular, globose, concentrically 

 striated, anterior lateral and cardinal teeth well developed, as in 

 Lucina, but the lunule is very deep, extending across the hinge- 

 area between the anterior lateral and the cardinal teeth. L. 

 Bichthofeni, Gabb (cxix, 46,53). Tertiary; California. Two 

 recent California species are included by Mr. Gabb in this group, 

 the main character of which is the excavation of the lunule. 



PARACYCLAS, Hall, 1843. May be a section of Lucina, but its 

 hinge and other internal characters are unknown. 5 sp. Devo- 

 nian ; N. Y. 



