• Peridinium oblongum : (Aurivillius) Cleve (1900)
• Peridinium divergens var. oblongum : Aurivillius (1898)
• Peridinium divergens: (Ehrenberg) Bergh (1882)

The cell is thecate,  solitary cell of medium dimensions, piriform and dorso-ventrally compressed. The cell surface appears reticulate. The apical pore is surrounded by a circular structure and the apical collar is made up of 5 parts. The apical plate 1’ has the  "ORTHO" shape, while the 2^nd apical intercalary plate is "quadra". The tilted cingulum divides the cell into two parts: the epitheca, which has concave sides and is prolonged into a long apical horn, and the hypotheca, which has two long thin divergent antapical horns, the left one in some specimens slightly shorter than the right one. The deep sulcus is decorated laterally by lists. 

Marine.

Distribution: as Peridinium divergens: Europe: Romania (Caraus, 2002).

As Protoperidinium oblongum: Europe: Great Britain (Parke & Dixon, 1976), Ireland (Gribble & Anderson 2006, Gribble & Anderson, 2007); South America: Chile (Alves-de Souza, Varela, Navarrete, Fernández & Leal, 2008 ).

The algae of Romania., Studii si Cercetari, Universitatea Bacau, Biologie 7, Caraus I., 2002, 1-694

Check-list of British marine algae - third revision., Journal of the Marine Biological Association of the United Kingdom 56, Parke M., Dixon P.S., 1976, 527-594.

High intraindividual, intraspecific, and interspecific variability in large subunit ribosomal DNA in the heterotrophic dinoflagellates Protoperidinium, Diplopsalis, and Preperidinium (Dinophyceae)., Phycologia 46(3):, Gribble K.E., Anderson D.M., 2007, 315-324

Molecular phylogeny of the heterotrophic dinoflagellates, Photoperidinium, Diplopsalis and Preperidinium (Dinophyceae), inferred from large subunit rDNA., Journal of Phycology 42:, Gribble K.E., Anderson D.M., 2006, 1081-1095

Distribution, abundance and diversity of modern dinoflagellate cyst assemblages from southern Chile (43-54oS)., Botanica Marina 51:, Alves-de-Souza C., Verela D., Navarrete F., Fernández P., Leal P., 2008, 399-410