Acila divaricata

Acila divaricata (Hinds, 1843) (Fig. 2 A, B) Nucula divaricata Hinds, 1843: 97. Acila (Acila) divaricata (Hinds, 1843) — Lutaenko & Noseworthy 2012: 21, pl. 1, figs. A–F. Material examined: three specimens from the Kunashirsky Strait (200 m). Distribution: South China Sea; East China Sea; Sea of Japan; southern Sea of Okhotsk; Kunashirsky Strait (20–500 m) (Scarlato 1981; Kurozumi & Tsuchida 2000, 2017; Kantor & Sysoev 2005; Liu 2008; Okutani, Saito & Haga 2009; Huber 2010; Lutaenko & Noseworthy 2012; Lee 2014; Zhang et al. 2014). Remarks: This is a new record from the region of the Kuril Islands. Zhang et al. (2014) noted that the subspecies Acila divaricata vigilia Schenck, 1936, was found in the Sea of Japan and off the Russian coast. Huber (2010) and Chinese researchers (Zhang et al. 2014) consider it as a separate species Acila vigilia Schenck, 1936, on the basis of morphological analysis of the type material only. Furthermore, Huber (2010) and Zhang et al. (2014) noted that Acila divaricata (Hinds, 1843) is distributed in the Philippines. This is explained by the fact that another subspecies, Acila divaricata balabacensis Schenck, 1936, was synonymized with A. divaricata on the basis of viewed photographs of the type material only. We are inclined to the opinion of Russian and Japanese malacologists (Scarlato 1981; Okutani, Saito & Haga 2009; Lutaenko & Noseworthy 2012) that A. divaricata occurs in waters of Japan and Russia. We suggest that A. divaricata, A. d. vigilia, and A. d. balabacensis need further study to determine their status and distribution. Acila divaricata is clearly distinguished from the eastern Pacific Acila castrensis (Hinds, 1843) by having a distinct radial fold and a rostrum at the posterior end of the shell.