The author discusses dimorphism in Egorovella and his new genus Egorovellina. A new term, "marginal dimorphism," is proposed for dimorphism involving a broadening of the marginal surface, as contrasted with "velar" and "histial" dimorphism which refer to modifications of various types of carinal structures. The author suggests that this type of dimorphism may indicate that the males and females lived in different biotopes. Seven new species of Egorovella and the genus and two species of Egorovellina are described and illustrated
