INTRODUCTION The present paper deals with some morphological features found in the species of the genus Euchirella Giesbrecht, 1888, family Aetideidae. In the course of my studies on the genus, I noted that the structures situated on the anterior surface of the endopodites of the first pair of swimming legs, which will be described below, have never been given the attention they obviously deserve. In none of the principal works on Calanoida, e.g., Scott (1909), Sars (1924-25), Rose (1933), and Brodskii (1950) these structures are dealt with in the text. The same holds for the important reviews by Vervoort (1957, 1963), and Tanaka & Omori (1969). Although most authors somehow figure a row of spinules on the tubercle of the endopodite, their drawings are invariably too small to allow one to observe the proper situation on this segment. To my knowledge, Park (1968: 549) is the only recent author who mentions the row of spinules with a few lines in the text, namely in his description of Euchirella unispina Park. An exception in this respect should be made for the work by Giesbrecht (1892), who depicts, albeit also in rather small figures, the central hairs and the hairbrush (see below) in two of his drawings (Giesbrecht, 1892: pl. 15 figs. 11, 30). In his description of Euchirella females the same author refers to Undeuchaeta Giesbrecht, 1888, where he mentions the terminal brush of hairs, and from here to Aetideus Brady, 1883, where he devotes one line to the row of spinules on the tubercle (Giesbrecht, 1892: 239, 232, 218). Giesbrecht (1892) always describes the legs very carefully, mentioning all structures he observes. However, he only goes into details for the first