Simocephalus (Simocephalus) mixtus Sars 1903

Simocephalus (Simocephalus) mixtus Sars, 1903 Fig. 1F–J Sars 1903b: 174; Orlova-Bienkowskaja 2001: 56–58, Figs. 85–86, Pl. I, II, VI; Rogers et al. 2019: 678, Figs. 16.2.18 I; Korovchinsky et al. 2021b: 156–157, Figs. 46, 9. Material examined. Four juvenile parthenogenetic females from a pond at the Lake Permai, Ipoh, Perak (4.47728° N, 101.0492° E), 28.01.2018. The species has been recorded in Peninsular Malaysia only once (Mizuno & Mori 1970), and Idris (1983) did not include it in his monograph. Only juvenile females were present in the studied materials. Juvenile females (Fig. 1F) have no distinctive protruding backward dorsal margin, characteristic for large adult females. Studied specimens have typical of subgenus S. (Simocephalus) morphology of head (Fig. 1G) and postabdomen (Fig. 1I), with outer side of postabdominal claw bearing uniform thin setulae (Fig. 1J). Studied specimens have the morphology of posterior-dorsal valve prominence characteristic of the species (Fig. 1H). The species was recently found in Sabah State, East Malaysia (Sinev & Yusoff 2018). In South-East Asia, S. mixtus was recorded in the North-East Thailand (Maiphae et al. 2008) and in Hainan Island (Sinev et al. 2015). For detailed description, see Orlova-Bienkowskaja (2001). Two other species of S. (Simocephalus), S. (S.) vetulus (O. F. Muller, 1776) and S. (S.) vetuloides Sars, 1898 were also recorded in South-East Asia (Korovchinsky 2013), but no morphological descriptions were provided for them. According to Orlova-Bienkowskaja (2001), these species are distributed in temperate regions only, so their presence in the region is doubtful.