On the specific characters of the haddock (Gadus aeglefinus, Linn.), whiting (Gadus merlangus, Linn.); Gadus poutassou, Risso; Gadus argenteus, Guichenot; Gadus saida, Lepechin; Gadus ogac, Richardson with a key to the species of Gadus found in northern waters / by H. Chas. Williamson.