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During a survey of the diatom flora of the Adegoy River (Krasnodar Territory, Russia), an unknown Fragilaria species (Bacillariophyta) was found that could not be identified using the currently available literature and here we describe it as a new species. The morphology of Fragilaria irregularis sp. nov. was studied using light and scanning electron microscopy and compared to similar species including Fragilaria deformis, F. rinoi, F. septentrionalis and Fragilariforma bicapitata. It differed from these taxa in several characters. Most observed valves showed an irregular striation pattern, a feature not observed in other species. Other important differences include valve outline (linear with parallel margins) and stria density (7–14 in 10 µm, lower compared to all other species). The new taxon has a linear valve outline with parallel to weakly convex margins, subcapitate apices and a very irregular, coarse striation pattern.

Several species currently belonging to the genus Fragilariforma D.M. Williams et Round are known worldwide. This genus is mainly characterized by regular spacing of the uniseriate striae composed of round areolae bearing simple vela, and simple apical pore fields. A large number of species has been recognised for some regions of South America and tropical Africa, but few studies encompass type material and/or the morphological variation existing within populations of the different species. The aim of this study is to identify and describe the morphology of these species from tropical environments under light and scanning electron microscopy and using available type material. Nomenclatural issues are examined and clarified for five taxa: Fragilaria nitzschioides var. brasiliensis Grunow, F. undata var. brasiliensis C. Zimmermann, F. strangulata (Zanon) D.M. Williams et Round, F. telum J.R. Carter et Denny and F. rolandschmidtii Metzeltin et Lange-Bertalot. The type material of F. nitzschioides var. brasiliensis, housed in the Grunow Collection at the Naturhistorisches Museum Wien (W) was examined and its epitypification is proposed. One new species from the Amazon region Fragilariforma amazonica sp. nov. is presented and described here, while Fragilaria telum is formally transferred to the genus Fragilariforma.

The transfer of Fragilaria javanica Hustedt to the genus Fragilariforma D.M. Williams & Round is presented based on a detailed analysis of the type material from Java (Malay Archipelago) using light and scanning electron microscopy. The taxon is characterized by each areola covered externally with a rota, well-developed, simple apical pore fields composed of rounded poroids and located on both valve apices, denticulate spines with tips oriented towards the apices, and open girdle bands with valvocopulae bearing heavily silicified advalvar fimbriae. These features are all shared with species currently ascribed to Fragilariforma, although the spine shape and orientation, and girdle elements having two rows of areolae, along with valvocopulae with well-developed fimbriae are typical of F. javanica. Morphological, ecological and distribution data are presented and discussed based on available literature for this taxon.

Two new species of Fragilariforma, F. cassieae sp. nov. and F. rakiuriensis sp. nov., are described from material from New Zealand, with reference to populations found in Australia. The new species are similar in shape and size to Fragilariforma lata and F. hungarica var. tumida but are separated on the basis of areola and stria density, and shape. The distinguishing features of F. cassieae are a rhombic shape with narrow protracted ends, and striae with prominent areolae. In F. rakiuriensis, small forms are similar in shape to F. cassieae, but larger cells are elongated with a constriction at the centre. The striae are more widely spaced than in F. cassieae with a slightly irregular appearance and fine, closely spaced areolae. We discuss the relationships of the new species within the genus Fragilariforma, and also discuss the possible existence of further related taxa in the material examined, or marked shifts in form in their morphological progression during cell division. The two species desc...

We describe a new diatom species of the genus Eunotia from a karst pond in Maolan Town, a karst area in Moalan Nature Reserve, Guizhou Province, China, using light and scanning electron microscopy. The species is similar to Eunotia sudetica, differing in size and shape of the valves. Externally, the new species has striae contained in shallow, irregularly-shaped channels and individual areolae have narrow openings due to the presence of rimmed occlusions. A large external opening of the rimportula occurs at one end of each valve. Internally, the new species has alveoli covering the areolae, the alveoli are partial in some specimens, present only in the middle of the valve while they extend from the dorsal margin to the ventral margin in other specimens. This species has a large rimportula and pseudosepta. In addition to the differences in extent of the alveoli, specimens differ in that some are proportionately wider than others, in the narrower valves small spines are consistently present as well as a few, shortened striae on the dorsal margin. We compare this new species with others in the genus based on its morphological features, and note similar internal alveoli in a species assigned to the genus Fragilariforma.

Fragilariforma Hajósiae is re-described from Pantocsek’s specimens of Diatoma fossile; these specimens are from Deménd (Demandice, Slovakia). Nomenclatural issues are examined and clarified as the name Fragilaria fossilis has previously been invalidly used by Hajós (1973a) and the combination Fragilariforma fossilis (Pant.) Tanaka unavailable thus making it necessary to create a new name to effect the transfer of Pantocsek’s Diatoma fossile to Fragilariforma.