Difflugia chaquensis Vucetich, 1989

Diagnosis: Shell shape varies from ovoid to subspherical, with the anterior end truncated. Pseudostome large with five or six shallow lobes. It is surrounded by a thin, narrow rim that does not constitute a true collar, but clearly marks the limits of the pseudostome. Below it is a ring of eight to six more or less circular pores. In some specimens it is not possible to observe the complete ring, since, apparently, the wall elements tend to cover some pores. The shell wall is made up of small rounded granules and diatom frustules. These often make up ninety percent of the shell. The pseudostomal ridge is formed by homogeneous particles of very small size. The organic cement that joins the elements of the wall has a rather irregular shape. In a higher plane, a network 0.2 microns thick and 0.3 microns wide is observed that joins the adjacent exogenous particles. Below this network and through its openings, a much thinner-walled mesh with numerous extremely small openings can be seen. This design is not uniform; On the lower plane, in some areas of the shell, quite thick rings of organic matrix are formed that replace the structure in the form of a fine mesh. The shell is transparent, light gray and very fragile.

Dimensions: Vucetichv(1989): Shell length 129–144 µm; width 99-108 µm; aperture (from the top of one lobe to the opposite side) 48-60 µm; diameter of the pores 12-14 µm (n=30) .

Habitat: Freshwater. Type location: Laguna Barranquera, Province of Chaco, Brazil.

Remarks: The most similar species is Difflugia pentagonostoma Chardez, 1964. D. chaquensis is differentiated from that species by the lack of a neck and by having more marked pseudostomal lobes and a more variable number. On the other hand, the diatom frustules agglutinated perpendicularly to the shell that give D. pentagonostoma a very characteristic hirsute appearance are missing in the aboral region. The dimensions of D. chaquensis are larger and its outline is less spherical.