Pileus: 4.5 - 17.0 cm broad; parabolic to conic when young, becoming planar to depressed and finally funnel shaped when mature; margins striate, decurved when young, then straight, finally becoming arched, uplifted and undulating, even when young but crenate at maturity, at times cracking and eroded; surface dry to moist, smooth at times with minute bumps; cuticle peeling variously, not at all to all the way to the disc; variously coloured, beige to blond, olive to grayish yellow, brownish orange, olive to violet brown, greyish green; context 1 cm at junction of stipe, firm, brittle, white, bruising yellow brown; taste mild; odour distinctive, fish-like, shrimp-like.
Lamellae: Horizontal or notched at first then decurrent and occasionally appearing free when mature; crowded at first then distant; when mature 1 cm wide, broad, edges even at times forking at stipe; colour white at first then pale to light yellow when mature, bruising brownish yellow to light brown; no lamellulae.
Stipe: 2.5 - 11 cm long X 1.5 - 4.0 cm wide, equal but at times tapering upwards; surface dry, unpolished, striate to grooved; colour white, occasionally with a pink flush at the base, becoming yellow brown when handled; context solid, spongy to chalky, white, bruising brownish orange to brownish yellow; surface and context turning blue green with FeS04.
Comments: This is an extremely variable mushroom, having brown, red or green cap colours. It is recognized by the fishy odour, mild taste, yellow spore print and the blue green colours when FeS04 is applied to the surface and context . It does not change red then black like R. occidentalis, and R. aeruginea differs by not changing at all when bruised.
Arora, D. 1986. Mushrooms Demystified. Ten Speed Press. Berkeley, Ca. pp 958.
Thiers, H.D. 1997. The Agaricales (gilled fungi) of California. 10. Russulaceae I. Russula. Mad River Press. Eureka Ca. pp 158.