A survey of the Sumatran Ctenidae (Araneae). 1. Two new Acantheis species Author Fomichev, Alexander A. Altai State University, Lenina Pr., 61, Barnaul, RF- 656049, Russia & Tomsk State University, Lenina Pr., 36, Tomsk, RF- 634050, Russia Author Omelko, Mikhail M. Federal Scientific Center of East Asia Terrestrial Biodiversity, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690022, Russia Author Marusik, Yuri M. Altai State University, Lenina Pr., 61, Barnaul, RF- 656049, Russia & Department of Zoology & Entomology, University of the Free State, Bloemfontein 9300, South Africa & Institute for Biological Problems of the North, Magadan 685000, Russia text Zootaxa 2023 2023-10-09 5353 2 117 130 http://dx.doi.org/10.11646/zootaxa.5353.2.2 journal article 10.11646/zootaxa.5353.2.2 1175-5326 8427062 7A24DCBF-BC93-4B25-BB8A-DEAE75167DB4 Acantheis dimidiatus ( Thorell, 1890 ) Figs 36–48 Acanthoctenus dimidiatus Thorell, 1890: 134 (♁). Acantheis dimidiatus Simon 1897: 117 . Material examined. 1♁ ( holotype ) ( MSNG ), INDONESIA : Sumatra Island: Singalong, O . Beccari. Examined by photo . Diagnosis. The species is similar to A. laetus from Kalimantan and to A. sergeimishenini sp. n. and A. andreimishenini sp. n. from Sumatra in having the slender embolus ( Em ), the medially located tegular apophysis ( TA ) and the elongated cymbial tip. The male of A. dimidiatus differs from that of A. laetus by by the strongly curved embolus ( vs . smoothly rounded, cf. Fig 43 and Lehtinen 1967 : fig. 410).The male of A. dimidiatus can be distinguished from that of A. sergeimishenini sp. n. by the non-bifurcated retrolateral tibial apophsis ( RTA ) ( vs . bifurcated, cf. Figs 41 and 15 ), the triangular tegular apophysis ( vs . comma-shaped, cf. Figs 43 and 23 ), and the ventral embolic branch twice thinner than dorsal one ( vs . ventral embolic branch twice wider than dorsal one, cf. Figs 41 and 30 ). From the males of A. andreimishenini sp. n. those of A. dimidiatus differs by the dorsal surface of opisthosoma with a thin stripe reaching spinnerets ( vs . wide cardiac mark reaching middle part of opisthosoma, cf. Figs 36 and 3 ), the median band on the carapace as wide as distance between PME ( vs . as wide as the distance between PLE), the triangular tegular apophysis ( TA ) ( vs . circular, cf. Figs 43 and 27 ), and the ventral embolic branch twice thinner than dorsal one ( vs . dorsal and ventral embolic branches equal in size, cf. Figs 41 and 31 ). For a complete list of the differences between the males of A. dimidiatus , A. sergeimishenini sp. n. and A. andreimeshenini sp. n. see Table 7 . Description. Male palp as shown in Figs 37–43 . Tibia ca. 4.6 longer than wide, 4 very long spines, longest ca. 0.7 of tibia length. Retrolateral tibial apophysis small, non-bifurcated. Cymbial tip about 0.42 of its length, slightly shorter than bulb. Sperm duct clearly visible only in retrolateral view. Tegular apophysis triangular. Embolus strongly curved. Ventral branch of embolus twice thinner than dorsal one. Female. Unknown. Distribution. Only known from the type locality ( Figs 46–48 ).