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LUCINIDAE 387
thick-shelled, white, and very finely sculptured. Somewhat like L. amiantus,
but without radial ribs, except for exceedingly fine threads seen best near
the beaks. Concentric sculpture of numerous, rather irregular, growth
threads. The shell commonly continues growth after a long rest, thus caus-
ing an irregular, concentric hump in the shell. Inner margin very finely
denticulate. P. crenella Dall is the same species. Common from beach to
1 20 fathoms.
Lucina tenuisculpta Carpenter Fine-lined Lucina
Bering Sea to Lower California.
Figure ySh
V2 inch in length, slightly less in height, oval in outline, chalky-white
and with a thin, grayish or yellowish green periostracum. Sculpture of nu-
merous, small, weak, raised, radial threads. Concentric growth lines fine and
irregularly placed. Beaks fairly prominent and pressed closely together. Be-
hind them, the narrow, depressed ligament is visible from the outside. In
front is the small, heart-shaped, depressed lunule. Inner margin of valves
finely toothed. Common just offshore.
Lucina approximata Dall Approximate Lucina
Monterey, California, to Panama.
Figure ySg
M inch or less in size. Very similar to tenuisculpta, but smaller, almost
round in outline, more inflated and with fewer and quite strong, radial rib-
lets. Periostracum very thin, commonly worn off. Shell texture less chalky.
Common in sandy mud just offshore to 48 fathoms.
Subgenus Fleurolucina Dall 1901
Lucina leucocyma Dall Four-ribbed Lucina
North CaroHna to southeast Florida and the Bahamas.
Figure ySd, e
Vi inch in length, roughly oval, fairly thick-shelled, inflated and white
in color. With 4 conspicuous, large, rounded, radial ribs, and with numerous,
small, crowded, squarish, concentric riblets. The inner margins of the valves
are finely denticulate. A common, bizarrely sculptured species found from
low water to several fathoms.
Subgenus Fseudomiltha P. Fischer 1885
Lucina floridana Conrad Florida Lucina
West coast of Florida to Texas.
Plates 38i, 3oaa