Pteriidae and Ostreidae 41 



Genus PTEKIA Scopoli, 1777 

 Pteria-'* coljuibus (Roding) PI. 4, fig. 17 



Average alt., 35; length, 55 mm., many individuals exceed these 

 dimensions. Shell is mequivalve, inequilateral, eared, obliquely winged 

 toward posterior; color brown with lighter, radiating bands; fresh 

 shells have a light-colored periostracum, lamellar in growth, with 

 spiny projections along the light radiating bands often extended in a 

 fringe beyond the shell margm; umbos well anterior to middle, not 

 projecting above cardinal margin; ventral margin oblique, rounded, 

 byssal notch near anterior ear; posterior margm concave; hinge 

 margin straight with posterior ear short or greatly elongated; two 

 small cardinal and one lateral tooth in each valve; a smgle muscular 

 impression, large, almost central; interior of valves nacreous, pearly 

 lining does not extend to free margins; byssus of silky, brown threads. 



Common on beaches. Dredged in three to seven fathoms. 



Genus PIJVCTADA Roding, 1798 

 Pinctada radiata-'* (Leach) PI. 4, fig. 18 



Average alt., 45; length, 43 mm. Shell somewhat quadrate, 

 slightly oblique; thin, flattened, byssal notch under anterior ear of 

 right valve; posterior ear not defined from posterior margin; outer 

 layer of shell laminated, with scaly projection concentrically ar- 

 ranged; this ornamentation is lacking in many specimens; brownish 

 color; occasionally a fine green color replaces the brown tone; smgle 

 lateral tooth in left valve, double laterals in right; interior nacreous; 

 wide, polished border about margins. 



Common on beaches. Dredged with Pteria colymbus. 



Family OSTREIDAE 



Ancient kitchen middens composed mainly of oyster shells and 

 found in many parts of the world which were inhabited by primi- 

 tive man testify to the importance of this mollusk in the economy of 

 that era, and no mollusk of our own time enjoys greater gastronomic 

 popularity. Oyster culture has a record and a tradition from the first 

 century B.C., and the patrician Roman of that time was able to dis- 



-* Gr., pteron, wing; kolymbos, a diver. 



-5 Span., pitttado, marked with spots; Lat., radius, a ray, rayed. 



