Indonesian chitons of the genera Belknapchiton Sirenko, Saito et Schwabe, 2022 and Leptochiton Gray, 1847 (Mollusca: Polyplacophora: Leptochitonidae) Author Sirenko, B. I. text Ruthenica, Russian Malacological Journal 2023 2023-04-03 33 2 79 94 http://dx.doi.org/10.35885/ruthenica.2023.33(2).4 journal article 10.35885/ruthenica.2023.33(2).4 2307-7336 11041944 Leptochiton rissoi ( Nierstrasz, 1905 ) Lepidopleurus rissoi Nierstrasz, 1905: 6 , figs 5, 52–55; Fer- reira, 1979: 163, figs 30–32. LLeptochiton ( Leptochiton ) rissoi . – Kaas, Van Belle, 1985: 110 , fig. 48, map 24. Type material. Lectotype ( ZMA .MOLL 138601), designated by Ferreira, 1979 . FIG. 11. Leptochiton commandorensis Banda Sea , Indonesia, 3200 m, BL–13.0 mm. A. Dorsal and ventral scales and marginal needles. B, E. Radula. C. Dorsal scales. D. Dorsal scales and needles. РИС. 11. Leptochiton commandorensis , море Банда, ИндонеЗиЯ, 3200 м, BL–13,0 мм. A. Дорсальные и вентральные че- Шуйки и маргинальные иглы. B, E. Радула. C. Дорсальные чеШуйки. D. Дорсальные чеШуйки и иглы. Type locality. Celebes Sea , N of Manado , Indonesia , 3°27.1’N 125°18.7’E , 2053 m ( Siboga , St. 126) . Distribution. Indian Ocean (off Sumatra Island), Pacific Ocean, Philippines , Indonesia , New Guinea , Solomon Islands , 875–2120 m , more common deeper than 1000 m . Remarks. The following morphological features of the lectotype were not mentioned in Nierstrasz [1905] and Kaas and Van Belle [1985] : the head valve is 1.2 times wider than the tail valve; the apophysis of the valve V is 1.3 times wider than the jugal sinus; the tegmentum granules are oval on the central area and round on the lateral areas with one megalaesthete and 6 micraesthetes; The head of the major lateral tooth of the radula is bidentate instead of unidentate as mentioned in Kaas, Van Belle [1985] . A study of the lectotype of this species ( ZMA . MOLL 138601) and other available specimens indicate that the number of aesthetes in an aesthete group ranges from 6 to 20, regardless of body size. This variability together with a longitudinal arrangement of the granules is similar to L. vietnamensis Sirenko, 1998 . The main difference between both species is the ratio of the width of the apophysis to the width of the jugal sinus, which is always greater than 1 in L. rissoi (vs less than 1 in L. vietnamensis ).