Halecium diminutivum Fraser, 1940a

Calder, Dale R. & Choong, Henry H. C., 2018, Names of hydroids (Cnidaria, Hydrozoa) established by Charles McLean Fraser (1872 - 1946), excluding those from Allan Hancock Expeditions, Zootaxa 4487 (1), pp. 1-83 : 31

Halecium diminutivum Fraser, 1940a

Halecium diminutivum Fraser, 1940a: 578 , pl. 33, figs. 6a, b.

Holotype. USNM 43438 : USA, Massachusetts, Nantucket Shoals , on Sertularella sp., one colony, 1.2 mm high, in fair condition, without gonothecae, labelled “ type ”; ethanol.

Schizoholotype. BCPM 976-00474-001 : USA, Nantucket , on Sertularella sp., one colony fragment, in fair condition, without gonothecae; slide.

Type locality. USA, Massachusetts: on Nantucket Shoals , epizoic on Sertularella ( Fraser 1940a) .

Current status. Valid.

Remarks. The “ type ” of Halecium diminutivum , as designated by Fraser (1940a), is justifiably listed as a holotype in the online database of the NMNH (USNM 43438). Several other species of hydroids occur with the holotype, including sertulariids, sertularellids, symplectoscyphids, and campanulariids. A slide of the species, from the same sample and on the same substrate (a species of Sertularella ), exists in the Fraser Hydroid Collection at the RBCM (BCPM 976-00474-001). With the species having been based on a single specimen ( Fraser 1940a) from Nantucket Shoals, and with no subsequent records of the species having been reported from the type locality ( Fraser 1944a, 1947a), we consider the RBCM material to be a fragment of the holotype (i.e., a schizoholotype).

This is a miniscule (to 1.2 mm high), easily overlooked, and poorly known species, reported only from two locations (the type locality of Nantucket Shoals, and also off Chatham Light) on the coast of Massachusetts, USA ( Fraser 1944a). The gonosome has yet to be described. Halecium diminutivum is held to be valid in Cairns et al. (2002) and WoRMS.