(Fig. 8)
Material examined. 11 specimens, ZRC.CNI.1357 (REL331–337, REL339), Pulau Ubin Jetty, Singapore, coll. R. M. Oh, January 2018.
Description. Body smooth, with visible longitudinal white lines spanning the entire column. Body column uniform in colour: purple, rust red, yellow, orange or blue. Body column short. Mouth outline round, elevated at the disc centre. Tentacles arranged in three or more circles of increasing radius around mouth (den Hartog et al., 1993). All tentacles translucent, ending in rounded, beige-coloured acrospheres (Acuña & Garese, 2009). Diameter of tips ranges from 15 to 20 mm. Mesenteries can be complete or incomplete. Often found in groups of three or more individuals.
Remarks. These animals may represent an undescribed species, but more extensive collections in the region will help ascertain its status in relation to other nominal species. Corynactis sp. most closely resembles Corynactis caribbeorum but is differentiated by a uniformly coloured, highly mutable body column lacking a distinct scapulus. Furthermore, Corynactis caribbeorum is found in the Caribbean and Atlantic Ocean near north Africa (Fautin, 2016).
Locally, Corynactis sp. is commonly known as the ‘balltip’ corallimorpharian from its distinct acrosphere shape, and is widespread in the intertidal habitats of both northern and southern shores in Singapore (Table 2). During low tide, its body column envelops the tentacles and oral disc. Once submerged the body column retracts and tentacles are fully extended. Individuals are identified in the field by its uniformly coloured, mutable body form adhering to common substrata including coral rock and granite pillars, and could be easily removed from the substrata.