The genus Hazenia H.C.Bold was described by Bold (1958: 742) to accommodate a single species, Hazenia mirabilis H.C.Bold, isolated from a pool near Nashville, Tennessee, USA, and characterized by irregularly branching uniseriate or partially multiseriate filaments, surrounded by a mucilaginous envelope. Škaloud et al. (2013: 1288) described a second species, H. broadyi Škaloud, Nedbalová, Elster & Komárek, from a shallow lake on James Ross Island, NE Antarctic Peninsula, and proposed a new combination, H. basiliensis (Vischer) Škaloud, Nedbalová, Elster & Komárek for Pseudendoclonium basiliense Vischer based on morphological and molecular evidence. Since its description, the genus name Hazenia has become well established in the literature (e.g., Bourrelly 1966; Broady 1979; Ettl & Gärtner 1995; Leliaert et al. 2015; Printz 1964; Škaloud et al. 2013; Starmach 1972). The genus Chamaetrichon Tupa was described by Tupa (1974: 69) with the type species C. capsulatum Tupa isolated from a liverwort in a lake in Sam Houston National Forest, Texas, USA. Darienko & Pröschold (2017) demonstrated the close affinity of C. capsulatum to various Hazenia species. In addition, they noted that no type specimen was designated for the type species of Hazenia (H. mirabilis) (ICN Melbourne Code Art. 40.1; McNeill et al. 2012), and because the genus name and its type species were described in one diagnosis (ICN Melbourne Code Art. 38.5), they concluded that Hazenia, H. mirabilis, and all proposed combinations are invalid. Darienko & Pröschold (2017: 33) therefore placed Hazenia under synonymy of the later described Chamaetrichon. However, we feel that this decision was incorrect because both the genus and species were validly described. Bold (1958) described Hazenia mirabilis based on solid morphological evidence, and although he did not explicitly designate a type, he deposited a living isolate to the UTEX Culture Collection and a herbarium specimen to the Chicago Natural History Museum (now The Field Museum). The herbarium specimen (Fig. 1) is currently located in the New York Botanical Garden Herbarium (NY), under accession number NY 03206340. According to ICN Melbourne Code Art 40.3, such a mention of a single specimen or gathering is acceptable as indication of the type, even if that element is not explicitly designated as type. In addition, Bold (1958) clearly indicated the locality and year of sampling, and stated that he was the collector of all material cited in the paper, which is also acceptable as indication of the type (ICN Melbourne Code Art 40, Note 2). Oddly, the date of sampling is indicated differently in the paper (April 1953) and on the herbarium specimen (March 1953). However, as only a single herbarium specimen of Hazenia mirabilis is deposited in NY (Laura Briscoe, pers. comm.), and since this specimen is marked as “Type specimen, Hazenia mirabilis gen. et sp. nov.” (Fig. 1), there can be no doubt that it represents the holotype as designated by the Bold. For the sake of taxonomic stability, we here indicate the holotype and designate as epitype the illustrations in the original publication (ICN Melbourne Code Arts 9.2 and 9.8.). Since Hazenia is a valid genus name, later described new species and combinations (H. broadyi Škaloud, Nedbalová, Elster & Komárek and H. basiliensis (Vischer) Škaloud, Nedbalová, Elster & Komárek (Škaloud et al. 2013)) are also valid. In addition, as Chamaetrichon capsulatum, the type of Chamaetrichon, belongs to the genus Hazenia (Darienko & Pröschold 2017), we here propose a new combination H. capsulata (Tupa) Škaloud & Leliaert, comb. nov. Accordingly, Chamaetrichon is a taxonomic synonym of Hazenia.