Stenostomum arevaloi Gieysztor, 1931

(Fig. 5 A, B, 7 A–C)

Localities. Loc. 9, 14.

Known distribution. France, Italy, Germany (Lanfranchi & Papi 1978), Spain (Gieysztor 1931), Poland (Kolasa 1973), North America (Nuttycombe & Waters 1938; Kolasa 1991), Brazil (Marcus 1945b), East Africa (Young & Kolasa 1974).

Material. Several individuals studied alive.

Description and remarks. The three pairs of light-refracting organs are as described by Marcus (1945a) and Young & Kolasa (1974): the first and second pair is simple whereas organs of the third pair are formed by two spheres (fig. 7B). However, Gieysztor (1931) described the organs of the third pair as being formed by four and up to six spheres. The epidermal inclusions are composed of two and up to seven spheres (fig. 7C). One specimen with eggs was found.