Genus Ervilia Turton 1822 Shell small, concentrically striate, and sometimes brightly hued. Liga- ment absent; resihum small and internal. Laterals small. Left cardinal large and bifid or split. Ervilia concentrica Gould Concentric Ervilia North Carolina to both sides of Florida and the West Indies. %6 of an inch in length, % as high, elliptical in outline, moderately com- pressed, although some are somewhat inflated. Each end is rounded to the same degree, and the beaks are central. There is a pinpoint depression just behind the glossy, inroUed beaks. Sculpture of fine, numerous concentric ridges. Radial threads may be present to form tiny beads. Color white, yellow or commonly with a pink blush. Common just offshore to 50 fathoms. E. rostratula Rehder from Lake Worth, Florida, is similar, but the posterior end is slightly more pointed. Family HIATELLIDAE Genus Hiatella Daudin 1801 Shell irregular due to nestling and burrowing habits. Texture chalky. No definite teeth in the thickened hinge of the adults. Pallial line discon- tinuous; siphons naked and slightly separated at the tips. Saxicava Fleuriau 1802 is the same. Hiatella arctica Linne Arctic Saxicave Figure 92a Arctic Seas to deep water in the West Indies. Arctic Seas to deep water off Panama. PKODISSOCONCH
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Figure 92. The young shells of Hiatella reared under the same artificial conditions. a, Hiatella arctica Linne; b, H. striata Fleuriau. (After M. Lebour 1938.) Generally i inch in length, but rarely 2 to 3 inches. A very variable species in its shape. The young are rather evenly oblong, but the adults become oblong, oval or twisted and misshapen. The shell is elongate with
