Parasitic elements in feces of Crotalus triseriatus from Mexico: (1) Egg of Capillariidae sp. with one larva (L), brown color, thick and rough wall (W), one operculum at each pole (Op), which are asymmetrical. (2) Sporulated oocyst of Eimeria sp., spheroidal type, rough outer wall (W), absence of micropyle, ovoid sporocysts (S). Scale bars: 10 µm.