Page:Pennsylvanian invertebrates of the Mazon Creek Area, Illinois Eurypterida.djvu/29

 pl. 1, figs. 1, 2) recorded a leg from the marine Namurian of Czechoslovakia. They named this form Stylonurus? (Ctenopterus?) ostraviensis and indicated its possible affinities to Ctenopterus. It now might

be preferable to questionably refer the Czechoslovakian species to Mazonipterus. It must be admitted, however, that the incongruous Czechoslovakian form reveals distinct carcinosomatid traits, although very little, if anything, is known of this family after the Silurian. Nevertheless, the morphology of the leg of M.(?) ostraviensis recalls forms such as Echinognathus and Carcinosoma. The marine occurrence of the Czechoslovakian form is certainly more indicative of the Carcinosomatidae than the Stylonuridae, a family that occupied more brackish-water habitats (see Kjellesvig-Waering, 1961, pp. 793–794).

Holotype.—United States National Museum no. 41169 a and b.

Diagnosis.—Carapace elongated and campanulate; lateral eyes large, arcuate, with round palpebral lobes and located intramarginally, but forward on the carapace.

Description.—The holotype and only known specimen consists of part and counterpart of a rather well-preserved, nearly complete