Description: Family Glycymerididae is one of the few local families which have taxodont dentition (photo). They typically have thick shells and also have an external hinge ligament (photo), radial ribs (photo), and their length is about the same as their height. Glycymeris septentrionalis has well-developed radial ribs that often look worn (see photo above). The taxodont dentition is about 15 teeth total, with the groups anterior and posterior to the central hinge clearly separated from each other. It also has pronounced tooth-like ridges along the inner ventral margin of the shell (see photo above). The beaks (umbones) are nearly central and the hinge line, which occurs at the same place, is arched instead of straight. The outside of the shell has a thick, dark brown periostracum which may be worn off except along the ventral margin. The interior of the shell may have yellow or purplish-brown areas. Length up to 4.5 cm.
How to Distinguish from Similar Species:Glycymeris corteziana is a rare species which is also subtidal but has very faint to microscopic radial ribs. It has about 20 taxodont teeth, with the anterior and posterior sets close together. Its periostracum is thin and tan. At first glance G. septentrionalis looks similar to the littleneck clam, Leukoma staminea, which also has radial ribs, a similar shell shape, and tooth-like serrations on the inside margins of the ventral shell margin. However, L. staminea does not have taxodont dentition at the hinge and is often found intertidally.
Geographical Range: Alaska to Baja California (uncommon in California)
Depth Range: Intertidal to 55 m (primarily subtidal)
Habitat: Sandy or gravelly bottoms
Biology/Natural History: Order Arcoida
is mainly tropical, and most have taxodont dentition.
Carlton, 2007 (briefly mentioned)
Kozloff, 1987, 1996 (as G. (Axinola)subobsoleta)
General Notes and Observations: Locations, abundances, unusual behaviors:
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Salish Sea Invertebrates web site provided courtesy of Walla