(Fig. 4)
Etymology. Latin pulposu s, fleshy, alluding to the fleshy form of the colony.
Material examined. Holotype: MBRBKH5, Yeonhwa-ri, Baengnyeong Island, 37.9461° N, 124.6267° E, intertidal, 18 May 2017. Paratype: MBRBKP5, same data as holotype.
Description. Colony forming large, rubbery gelatinous creamy-yellow-brown masses that develop bulbous lobes of varied breadth and projecting irregular branches from encrusting base on algal stems or other cylindrical substrata (Fig. 3A); growth extending up to 14–15 cm long along stem. Zooids erect, irregular in size and shape, oval to hexagonal, frontal surface flat to slightly convex, with small round orifice that forms a little papilla when closed; zooid wall somewhat translucent, so that whitish shape of polypide can be discerned in deep body of cystid (Fig. 4B, C, E). Beneath outer layer of autozooids is firm gelatinous core that resists being cut (Fig. 4F). Zooid length, mean 0.363 mm (range 0.306–0.393, N = 6); zooid width, mean 0.258 mm (range 0.216–0.306, N = 6), orifice diameter, mean 0.087 mm (range, 0.072–0.208 mm, N = 6)). Kenozooids abundant (Fig. 4B–D). Some zooids contained clusters of yellow eggs or embryos (Fig. 4B, C).
Remarks. None of the colonies collected expanded while observed, so that polypide characters could not be noted. The species is similar to Alcyonidium bullitum n. sp. in the presence of abundant kenozooids, but these are larger relative to zooid size than in A. bullitum This species shows similarities to Alcyonidium diaphanum (Hudson, 1778) from the Northeast Atlantic, but the lobes of the Korean species are larger and more rounded. Its closest relative may be Alcyonidium diaphanum alcilobatum d’Hondt & Mawatari, 1986 from Japanese Pacific localities and considered by them to be a new subspecies because of its geographic isolation from European populations. Its lobes are thinner and more leaf-like than those of A. pulposum n. sp., as shown in their paratype and holotype specimens (d’Hondt & Mawatari 1986, pl. 1, figs 1, 2). Colonies of A. pulposum n. sp. also lacked the small projecting bumps of incipient lobes seen in mature Belgian colonies of A. diaphanum illustrated by De Blauwe (2009, p. 43, figs 15, 16).
Distribution. Yellow Sea: Yeonhwa-ri, Baengnyeong Island, where subtidal colonies were washing up in the surf zone.