Based upon a large collection from the western Mediterranean, a description of a new genus of notodelphyid parasitic copepod from didemnid ascidians is given. The new genus Anoplodelphys is erected for three new species found in different host species. Anoplodelphys clearly belongs to the ophioseidimorph group of notodelphyids ; within this group, the genus is mainly distinguished by the complete lack of true buccal appendages, feature in common with only four previously described species. The discovery of this new genus increases the polyphyletic trend within the ophioseidimorph notodelphyids. The host specificity is extremely narrow : all three new species of Anoplodelphys live in several species of the large genus Didemnum. Some remarks on the host parasite relationships conclude the paper. [NOT CONTROLLED OCR]