MORPHOLOGICAL STUDIES OF AULACODISCUS SPECIES FROM THE “RUSSIAN COLLECTION” OF THE CALIFORNIA ACADEMY OF SCIENCES

Abstract

Our investigation focused on the morphology of Aulacodiscus species from the Russian sediment samples curated at the California Academy of Sciences, mostly from the localities of Kamishev, Carlovo, Ananino and Singelievsky. Our observations suggest that useful characters potentially defining infrageneric taxa include valve relief, shape and position of the external tubes of the rimoportulae, shape of the internal expression of the rimoportulae, shape and orientation of the internal rimoportula slit, structure of the areolae and vela and presence or absence of bullulae in the wall.