Slaty-backed Nightingale Thrush

It measures 17 cm. and weighs 35 grams. is the darker of the Catharus , the iris is pale.
Adults are dark gray above, and become black slate in the head, wings and tail. The throat, breast, sides, flanks and crissum are slate gray, the center of the lower chest and abdomen are white. The iris is pale gray. The eye ring and beak are orange, The legs are paler orange.