Non-blue <i>Haslea</i> species (Bacillariophyceae: Naviculaceae) in the benthic marine flora of Guam (Mariana Islands, Western Pacific Ocean).

In recent years the taxonomy of <i>Haslea</i> has been in flux. We describe several <i>Haslea</i> taxa from Guam, including four new species, in light of these recent findings. Four delicate, fusiform <i>Haslea</i> species are described from a variety of benthic habitats on coral reefs. These species, <i>H. fusiformis</i> comb. nov. and <i>H. alexanderi, H. apoloniae</i> and <i>H. guahanensis</i> spp. nov. are distinguished by stria density, foramen (‘areola’) shape, and cell size from each other and from similar taxa. A key to all these taxa is provided. In addition, an arcuate species is described as <i>Haslea arculata</i> sp. nov. The presence of a bilayered wall is shown for all these taxa. We compare the morphology of specimens reported as <i>H. howeana</i> from Guam with <i>Navicula tsukamotoi</i>, recently described from Okinawa, and with ‘<i>Navicula</i> cf. <i>howeana</i>’ from Puerto Rico. We provide the first account of the complex cingulum of <i>N. tsukamotoi</i>. We conclude that our specimens match <i>N. tsukamotoi</i> and that <i>H. howeana</i> should be returned to <i>Navicula</i>, but we leave open the question of conspecificity.