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Rh Color whitish to tan with purpUsh over the beak and posterior areas. PaUial sinus commonly, but not always, about the length of the posterior muscle scar. It points upward. This is a very common shallow-water species. A number of subspecies or forms have been described, but their vahdity needs clarification: purpurea Lea (fig. 84c to e), ?nanhattensis Prime and fretensis Rehder. Genus Parastarte Conrad 1862 Shell the size of a split-pea, very similar to Geimna. In Parastarte, the ligament is high and situated beneath the beak, occupying a very high and broad area. In Gemma, the ligament is very narrow and elongated, and ex- tending posterior to the beaks. PaUial sinus much smaller in Parastarte.

Figure 85. Brown Gem Clam, Parastarte triquetra Conrad, ^ inch (Florida). Brown Gem Clam Figure 85 Parastarte triquetra Conrad Both sides of Florida (to Texas?). % inch in size, very similar to Gemma geTfmta, but much higher than long, with the beaks larger and elevated. Exterior highly polished and smoothish. Color usually tan to brown, but may be flushed with pink in beachworn specimens. The pallial sinus is almost absent. Moderately com- mon on sand bars and obtained by screening the sand. Family PETRICOLIDAE Subfamily PETRICOLINAE Genus Petricola Lamarck 1801 Subgenus Naranio Gray 1853 Petricola lapicida Gmelin Boring Petricola South half of Florida and the West Indies. H inch in length (up to 1% inches in the Lesser Antilles), ovate, in- flated, chalk-white, with criss-cross, threaded sculpturing. Beaks swollen and