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 



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. 



