The structure of the receptor cells in the olfactory organ of the rays Raja clavata and Dasyatis pastinaca and spiny dogfish Squalus acanthias is similar to that of the olfactory cells in other Vertebrates, although their tops are invariably crowned by microvilli, not flagella. In the peripheral process of these cells of Elasmobranchs and some other vertebrates represent a special type of the olfactory receptors which originated as the result of differentiation of primary olfactory cells supplied both by flagella and by microvilli. In the olfactory epithelium of Elasmobranchs, together with the supporting cells crowned by cilia, numerous goblet cells were observed. These glands produce a mucus which protects the olfactory epithelium of Elasmobranchs from the direct contact with the sea water. Similar to that in all other vertebrates, this mucus represents an intermediate milieu for the molecules of odorous substances.