Freshwater Mussels Pacific Northwest - The Xerces Society

The Crooked River is home to populations of western ridged mussels. photo: Dennis Frates
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Western Ridged Mussel
Gonidea angulata (Lea, 1838)
Description 15,18
Size: Up to five inches
Shape: Obovate to trapezoidal. Slightly laterally compressed. The shell has
an angular ridge that runs from the beak to the basal part of the posterior
margin; this ridge may be less angular in specimens living in slow-moving
water. The ventral margin is usually straight. The shell is heavier than that of
all other native species.
Periostracum: Color yellowish-brown to brown or black. No shell rays or
sculpturing on the shell.
Lateral Teeth: Absent.
Pseudocardinal Teeth: The right valve has one small tooth and the left valve
has either one small tooth or none at all. The teeth are small and compressed,
sometimes hard to distinguish.
Nacre: Usually white, but sometimes salmon-colored in fresh specimens and
pale blue toward the posterior margin and beak cavity.
Range
Also known as the Rocky Mountain ridged mussel, this species is widely distributed
west of the Continental Divide from California to British Colum-
Freshwater Mussels of the Pacific Northwest