On Algodoal and Maiandeua Islands, a sandbank APA in the State of Pará, located in the municipality of Maracanã, the family Myrtaceae R. Br. is represented by the genera Myrcia, Eugenia, Myrciaria and Calycolpus, in a total of 15 species. In this paper, Myrcia DC. ex Guillemin was emphasized, with additional comparative comments on the taxonomy of the other genera. The identification of the species of Myrcia needed a careful revision, hence the emphasis on studying them. Samples with flowers and fruits were collected and analyzed beside exsiccata from the MG and IAN herbaria. The analysis was done under a stereomicroscope, in the classical procedures used in plant taxonomy. Myrcia is composed of about 300 species in tropical America, distributed in various ecosystems such as forest, cerrado, campo rupestre, restinga, etc.. The genus has an arboreal or shrub habit; axillary or terminal inflorescences, in panicles or summits, some species with flowers in pairs or triads; persistent bracts, bracteoles and calyces; pedicellate flowers, sepals 5, free, distinct; hypanthium prolonged or not over the ovary apex; petals 5; numerous stamens; ovary 2-4 locular and berry fruit with persistent sepals. In the studied restinga 6 species occur, which fall into 3 sections: I. Section Armeriela: Myrcia rufipila Me Vaugh, Myrcia speciosa (Amshoff) Me Vaugh; II. Section Aulomyrcia: Myrcia cuprea (Berg) Kiaerskou, Myrcia multiflora (Lamarck) De.; III. Section Myrcia: Myrcia sylvatica (G. Meyer) De. and Myrcia fallax (Richard) DC. Eugenia consists of 7 species, Calycolpus and Myrciaria of 1 each. Descriptions, identification key, illustrations, geographical distribution and comments on all Myrtaceae species from Algodoal and Maiandeua are presented.
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