Phascolosoma (Phascolosoma) arcuatum (Gray)

Figs 2 H, 3C

Phascolosoma (Phascolosoma) arcuatum Cutler, 1994: 163, 167, 170, 172, 176, fig. 49D (for complete synonymy).

Material examined. Nine specimens (NMNS-5928-012), Kaomei tidal flat (24°19.34' N, 120°33.11' E), Taichung County, high intertidal sandy mud bottom, coll. P.-W. Hsueh, 22 December 1992; three specimens (NMNS-5928-013), Kaomei tidal flat (24°19.34' N, 120°33.11' E), Taichung County, intertidal sandy mud bottom, coll. P.-W. Hsueh, 25 April 1999; 4 specimens (NMNS-5928-014), Kaomei tidal flat (24°19.34' N, 120°33.11' E), Taichung County, high intertidal sandy mud bottom, coll. P.-W. Hsueh, 8 March 2003; One specimen (NMNS-5928-015), Hambao tidal flat (24°00.23' N, 120°21.07' E), Changhua County, high intertidal sandy mud bottom, coll. H.-T. Hung, 11 July 2001; one specimen (NMNS-5928-016), Shenkuang tidal flat (24°09.50' N, 120°27.32' E), Changhua County, high intertidal sandy mud bottom, coll. H.-T. Hung, 11 July 2001; 7 specimens (NMNS-5928-017), Bajhang tidal flat (24°00.23' N, 120°21.07' E), Chiai County, high intertidal sandy mud bottom, coll. H.-T. Hung, 17 January 2007; One specimen (NMNS-5928-018), Fubao tidal flat (23°59.28' N, 120°21.05' E), Changhua County, high intertidal sandy mud bottom, coll. H.-T. Hung, 11 July 2001; 5 specimens (NMNS-3636-058), Yunsen (24°29.34' N, 118°32.44' E), Kinmen County, high intertidal sandy mud bottom, coll. H.-T. Hung, 21 February 2001.

Remarks. The external morphology of the present specimens agrees well with descriptions of the species in Cutler (1994); the species has large and dark papillae set off from the skin, the introvert is up to twice the trunk length, there are more than 100 complete and incomplete rings of hooks (about 40–70 um tall), basally with greatly expanded clear streak and it is without secondary teeth, warts, or toes (Cutler, 1994: 170, fig. 49D; present study, Fig. 3 C). It is commonly seen in the Indo-West Pacific region (from northeastern India to southern China) and known to tolerate brackish-water environments.