Original description: [Valensi, 1949, p. 547] (translated from French):

Micrhystridium cometes nov. sp.
6 of fig. 5.

Holotype: Lower Bathonian, flint from Airvault (Deux-Sevres).

The shell is ovoid with a large and a small end, it is covered with a hair of processes tightly packed against each other and undulous; their insertions distributed without order finely punctuate its surface. Here and there and at roughly regular intervals there is a stronger and thicker process; the processes are clearly shorter at the large end.

The holotype (6 of fig. 5) measures 19 μ in its greatest length and 1 μ in its smallest; the length of the processes is between 3 μ and 5.
The color of all specimens of this species is yellow.

I found four individuals of this species, three in the Lower Bathonian of Airvault, one in the Bathonian of Moulinet (Vienne); the latter has a circular outline with a diameter of 16 μ, and must correspond to an ovoid shape seen from one end, the other three specimens have dimensions between 11 and 13 μ.
No similar species has been described so far in other stages of the stratigraphic series.