Niphargus virei and N. schellenbergi (hypogean Gammarids) as also Gammarus pulex pulex (epigean Gammarid) show on the Gn1 and Gn2 of both sexes ornamented areas which were studied with a scanning electron microscope. The ornamentations are built up of teeth. These are simple in Gammarus pulex pulex and present a sexual dimorphism on the meropodite. In N. schellenbergi and N. virei they are as often as not grouped by three. In Orchestia (Talitrid) the teeth have their bases fusioned which forms pectinate scales showing a sexual dimorphism. Outside these areas, the gnathopod cuticle of N. virei, N. schellenbergi and Gammarus pulex pulex is ornamented with ovoid papilla, each of them surmounted by a finger-like process covering over a depression.