Mucous and oxynticopeptic cells in the gastric mucosa of the seps, Chalcides chalcides (Linnaeus, 1758) were examined by standard histochemical staining methods and by lectin histochemistry. The epithelial mucous cells lining the surface of the stomach and the mucous cells of the fundic glands elaborated mainly neutral glycoproteins with β(1,4)GlcNAc oligomers, GalNAc glycosidic residues and Galβ1,3GalNAc terminal sequences. The mucous cells of the fundic glands were stained specifically with the Paradoxical Con A method. The mucosecreting cells of the pyloric glands produced neutral glycoproteins, with β(1,4)GlcNAc oligomers, GalNAc residues and Galβ1,3GalNAc terminal sequences. Terminal L-fucose bound to the penultimate GlcNAc residues, and/or difucosylated oligosaccharides were also present. The pyloric glands did not stain with the Paradoxical Con A procedure. The morphology of the oxynticopeptic cells changes from the oral to the aboral region of the fundic mucosa. In the oral fundic tract the oxynticopeptic cells showed cytoplasm filled with zymogen granules, while in the aboral fundic region these cells contained few zymogen granules and showed cytoplasm full of empty vesicles, typical of the acid secreting cells. A secretion gradient of proteolytic enzymes and hydrochloric acid along the fundic mucosa of the seps can be hypothesised.