Proeuphractus Ameghino
Proeuphractus Amegh., 1886, Bol. Acad. Nac. Cienc. Cordoba, t. 9, p. 208.
This genus is seldom found, but is distinguished by Ameghino by the absence of a pelvic buckler, all the plates of the carapace being movable. From the Deseado beds, Ameghino describes two species, P. setiger and P. laevis, both based on isolated plates; the former distinguished by having no piliferous perforation in the furrows surrounding the central figure, and with well-developed pits on the posterior margin; while the latter has small piliferous perforations in the furrows and only rudimentary ones on the posterior margin. These features do not seem to me to distinguish species.
In addition to the foregoing, Ameghino has made a series of genera and species,[23] Archaeutatus, Amblytatus, Isutaetus, Sadypus, Hemiutaetus, Anutaetus, all based on isolated plates, and distinguished by variations in the central figure and the piliferous pits. I am unable to find a satisfactory basis for distinguishing the genera or species, and feel that, until more complete material is known, it is impossible to say which are valid genera or species.