388 American Seashells 



1/4 inches in length, almost circular, compressed, smoothish, except for 

 a few weak, irregular growth lines. Pure-white with a dull- whitish, flaky 

 periostracum. The beaks point forward, and in front of them there is a deep, 

 small pit. Hinge plate fairly wide and strong, but the teeth are weakly de- 

 fined. Moderately common in shallow water to a few fathoms. 



Genus Phacoides Gray 1847 



Shell orbicular, quite compressed. Sculpture mostly concentric. Cardi- 

 nal teeth obsolete in adults, but the laterals are well-developed. Phacoides 

 Blainville is the same but is not considered valid. Dentilucina Fischer is the 

 same. 



Subgenus Phacoides s. str. 



Phacoides pectinatus Gmelin Thick Lucina 



Plate 38g 



North Carolina to Florida, Texas and the West Indies. 



I to iVo inches in length, ovate, compressed, white or flushed with 

 bright-orange. Concentric ridges moderately sharp, usually unequally spaced. 

 Ligament partially visible from the outside. Lunule strongly raised into a 

 rather thin, rough blade. Anterior and posterior lateral tooth strong. Cardi- 

 nals very weak. Moderately common in shallow water. Alias Lucina ja- 

 maicensis Lamarck. Do not confuse with P. filosus. 



Subgenus Lucinisca Dall 1901 

 Phacoides nassula Conrad Woven Lucina 



North Carolina to Florida, Texas and the Bahamas. 



V^ inch in length, almost circular, inflated, strong and pure white. Sculp- 

 ture of strong, closely spaced, concentric and radial ribs. These form a 

 reticulate, rough surface. Where the ribs cross each other there is a tiny, 

 raised scale. The ventral margin of the valve is strongly beaded by the distal 

 ends of the axial riblets. Common in shallow water to 100 fathoms. 



Phacoides rmttalli Conrad Nuttall's Lucina 



Plate 3ig 



Santa Barbara, California, to Manzanillo, Mexico. 



I inch in length, circular, moderately inflated and with a fine, sharp, 

 cancellate sculpturing. The shell is divided off^ at the anterior and upper 

 portion into a slightly more compressed region which is less sculptured con- 

 centrically. Lunule very deep, short and larger in the left valve. Moderately 

 common offshore in sand. 



