The genus Onchocalanus G.O. sars, 1905 (Crustacea Copepoda)

The genus Onchocalanus was established by G. O. Sars in 1905 for two remarkable new Copepods, collected in deep water of the Atlantic Ocean, which were named Onchocalanus trigoniceps and Onchocalanus hirtipes. Of both forms the females only were found. Sars' generic diagnosis is very short; he only states that his new genus Onchocalanus is closely related to Xanthocalanus Giesbr., 1892, from which it differs by the shape of the rostrum, which in Onchocalanus is strongly chitinized and has a bifurcated apical portion, by the unusually strong, curved claw on the extremity of the 2nd maxilla, by the long and slender maxillipeds, and by the spinulation of the four pairs of swimming legs. In addition in the two genera there are minor differences in the shape of the 5th pair of legs. Undoubtedly the genera Onchocalanus and Xanthocalanus are closely related; the discovery of males of species of both genera has again underlined their relationship. Recently the number of species of these genera has considerably increased; it seems highly desirable, therefore, to re-establish the generic characteristics of Onchocalanus in its present, more extended form and to settle the identity and synonymy of its various species. This is the more desirable as some difference of opinion seems to exist about the limits of variation of certain species. Of the genus Xanthocalanus a much larger number of forms is known at present, in many instances described after mutilated, female specimens. A revision of this genus, although much needed, will undoubtedly meet with considerable difficulties. The present notes on species of Onchocalanus are based on specimens in the collections from the Siboga and Snellius Expeditions (eastern part of the Malay Archipelago), the Dana Expeditions (mainly on the Indo-pacific material) and on some Antarctic