Tonicellidae Simroth 1894

Family Tonicellidae Simroth, 1894 Genus Boreochiton Sars, 1878 Type species. Chiton ruber Linnaeus, 1767, by subsequent designation (Pilsbry 1893). Distribution. Boreochiton is known from the Pliocene to the Recent, and presently distributed mainly in the northern Pacific, with one species in northern Atlantic (Sirenko 2016). The fossil record includes the Pleistocene of North Atlantic (Hoel 1914; Antevs 1917, 1928), Netherlands (Strack 2010) and Italy (Dell’Angelo & Giusti 1997). Remarks. Sirenko (2000) reinstated the genus Boreochiton Sars, 1878, for some species originally attributed to the genus Tonicella, among which T. rubra (Linnaeus, 1767). The main feature of Boreochiton is the presence of a large fenestral gland in the tail of living individuals, only found in this genus. Boreochiton includes four species and one subspecies (Sirenko 2016; Sirenko & Dell’Angelo 2023). The main characters of Boreochiton ruber are included in Tab. 21.