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Genus Chattonia n. gen.
Type: Chattonia animula Marwick.
Shell small, hatchet-shaped, strong; beaks prominent, at anterior third or fourth; posterior end broadly truncated, bounded below by low ridge. Sculpture, of regular concentric grooves. Hinge of moderate width. Left hinge with two narrow, divergent, anterior cardinal teeth, anterior one much the stronger and well separated from raised lunular border. Behind these cardinals is a triangular ligamental space bounded posteriorly by long curved posterior lateral which extends two-thirds length of dorsal margin from which it is separated by a well-defined groove. Right hinge with long straight anterior lateral confluent with lunular margin above; cardinal tooth strong, posterior lateral long, curved. Internal margins smooth.
Chattonia animula n. sp. (Figs. 10, 11, 12.)
Holotype in Dominion Museum.
Height, 4.5 mm.; length, 5.3 mm.; inflation (1 valve), 1.25 mm. For description see generic diagnosis above. The specimens show considerable variation in shape, size, and coarseness of sculpture, so that further collecting may necessitate specific subdivision. The
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largest specimen is nearly 9 mm. long. The elements of the hinge are the same as those of Crassatellites, but this does not necessarily demand inclusion in that genus, for the crassatelloid hinge is an extremely conservative one. The small size, the curved dorsal margin, the shape of the lateral teeth, and the very narrow ligamental scar on the hinge deserve full generic recognition.