Page:American Seashells (1954).djvu/469

Rh 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 Figure ySh Bering Sea to Lower California. 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 Figure ySg Monterey, California, to Panama. 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 Figure ySd, e North CaroHna to southeast Florida and the Bahamas. 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 Plates 38i, 3oaa West coast of Florida to Texas.