210 LUCINIDA. 
SuspraMity LUCININA. 
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, Bruguiére, 1792. 
Etym.—Lucina, a name of Juno. 
Distr.—100 sp. Universal. Fossil, 250 sp. U. Silurian—; 
United States, T. del Fuego, Europe, Southern India. L. Jamat- 
censts, 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—1l 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. 
coycLas, Klein, 1753. (Divaricella, von Martens, 1880.) Valves 
divaricately striate ZL. divaricata, Lam. (exix, 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. UL. tigerina, Linn. (exix, 42). 
MILTHA, H. and A. Adams, 1856. Shell inequivalve, with 
nearly smooth surface; lateral teeth obsolete. L. Childreni, 
Gray (cxix, 43). 
MYRTEA, Turton, 1822. (Cyrachea, Leach.) Shell a little 
compressed, ribbed, crossed by scabrous concentric lines. Car- 
dinal teeth one in one valve, two in the other. JZ. scabra, Lam. 
(exix, 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. JL. 
Richthofeni, Gabb (cexix, 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, 1848. May be a section of Lucina, but its 
hinge and other internal characters are unknown. 5 sp. Devo- 
nian; N. ¥. 
