Hymedesmia (Ectyodesmia) mutabilis var. costata Topsent, 1928 (Fig. 7E) Hymedesmia (Ectyodesmia) mutabilis var. costata Topsent, 1928: 260, pl. VIII figs. 20, 22–23. The variety was described by Topsent for three specimens from two stations of Prince Albert 1 er taken near the Azores, Stat. 3150 and 3293, the first from 38.0167N 25.35°W at 1740 m depth, indicated by Topsent as the type (not identified, but presumably in MOM with a slide in MNHN). Topsent listed spicular differences with the typical variety Hymedesmia (H.) mutabilis (Topsent, 1904: 166 as Hymeraphia, collected from the Azores, Prince Albert 1 er cruises Stat. 597, 702 and 899, with that of Stat. 702 chosen as the type, 39.3556°N 31.098°W, depth 1326 m, type registration number not identified, but it is presumably in MOM with a slide in MNHN). The specimen from Stat. 899 was reassigned to the present variety by Topsent (1928: 261). The spicular differences with the typical variety were notably the ornamented shaft of the arcuate isochelae (smooth in the typical variety) and the stylote or mucronated shape of the tornotes (smooth tylotes in the typical variety). Since the specimens were collected from the same general area in the deeper North Atlantic near the Azores, I propose to elevate the present variety to a distinct species Hymedesmia (Hymedesmia) costata Topsent, 1928.

Published as part of Van Soest, Rob W. M., 2024, Correcting sponge names: nomenclatural update of lower taxa level Porifera, pp. 1-122 in Zootaxa 5398 (1) on page 68, DOI: 10.11646/zootaxa.5398.1.1, http://zenodo.org/record/10494167