This paper is concerned primarily with the taxonomy of two species of the copepod genus Botryllophilus (Ascidicolidae: Botryllophilinae) collected from compound ascidian hosts in Golfo di Napoli (= the Gulf of Naples). Both copepods belong to subgroup 2 of female morphotype A of the genus. The female of B. banyulensis Brément, 1909, living in the type host Parascidia areolata (Delle Chiaie), is redescribed, and the male is described for the first time. In the case of B. neapolitanus n. sp., living in Aplidium sp., the female is described. In subgroup 2, consisting of four species including the new species, the leg armature formulas are of pattern II, in which additional armature elements (setae, spines, etc.) are found on most legs; this differs from the armature formula of pattern I. Six species of subgroup 1 of morphotype A have pattern I. In this paper, it is shown that the four species of subgroup 2 exhibit four different formulas of pattern II; B. banyulensis has pattern II–1, and B. neapolitanus has pattern II–3. The original concept of morphotype A is revised in order to accommodate all the species of subgroups 1 and 2.