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 setiger ( Nierstrasz, 1905 ) Lepidopleurus ( Pilsbriella ) setiger Nierstrasz, 1905:11 , pl. 1, fig. 7, pl. 3, figs 60–65. Leptochiton ( Pilsbryella ) setiger . – Kaas, Van Belle, 1985: 161 , fig. 74, map 22. Type material. Lectotype ( ZMA .MOLL.138607) designated by Kaas and Van Belle [1985] , and 2 paralectotypes ( ZMA .MOLL.138606, ZMA . MOLL.138625) (see below). Type locality. Indonesia , Strait of Makassar, 0°34.6’N , 119°8.5’E , 1301 m . ( Siboga , St. 88) The paralectotypes were found in the Sea Bali , 7°15’S , 115°15’.6’E, 289 m ( Siboga , St. 12). Distribution. Only known from the type locality of the lectotype . Remarks. Sirenko [2020] already discussed the composition of the type specimens of this species. A thorough study of the lectotype and two paralectotypes revealed their morphological heterogeneity. The two paralectotypes differ from the lectotype in the arrangement of granules on the central areas in quincuncialy and in the absence of chitinous silky hairs between the valves, the main feature of this species, which served as the basis for the description of the subgenus Pilsbryella Nierstrasz, 1905 . They most likely belong to the genus Nierstraszella Sirenko, 1992 for a number of morphological features: 1) arrangement of false tegmentum granules in a quincunx pattern, 2) subcarinated valves, 3) elongated dorsal spicules-scales, 4) a tridentate cusp of the major lateral tooth, which is typical for juvenile individuals of Nierstraszella [ Sirenko, 1992 ] and 5) the paralectotypes were found on a piece of sunken wood which is a very typical substrate for Nierstras- zella . By the way, two species of chitons: Leptochiton longisetosus Sigwart et Sirenko, 2012 and L. dykei FIG. 14. Leptochiton commandorensis, Banda Sea , Indonesia, 3200 m, BL–5.0 mm. A. Dorsal and ventral scales. B, C. Radula. D. Major lateral and uncinal teeth of radula. РИС. 14. Leptochiton commandorensis , море Банда, ИндонеЗиЯ, 3200 м, BL–5,0 мм. A. Дорсальные и вентральные че- Шуйки. B, C. Радула. D. БольШой латеральный и унцинальный Зубы радулы. FIG. 15. Leptochiton commandorensis , Banda Sea , Indonesia, 3200 m, size 800 x 630 µm. A. Juvenile from pallial groove of female BL–5.0 mm, dorsal view. B. Dorsal scales and needles of the juvenile. РИС. 15. Leptochiton commandorensis , море Банда, ИндонеЗиЯ, 3200 м, раЗмер 800 x 630 мкм. A. Ювенил иЗ паллиального желобка самки BL-5,0 мм, вид сверху. B. Дорсальные чеШуйки и иглы ювенила. Sigwart et Sirenko, 2012 [Sigwart, Sirenko, 2012] have long silky intersegmental bristles very similar to the hairs described by Nierstrasz for Lepidopleurus ( Pilsbryella ) setiger .