Page:A Revision of the Families and Genera of the Stylonuracea (Eurypterida).djvu/29

 marginal rim very narrow, simple, not ornamented; ornamentation smooth; no other parts known.

Type species.—Mazonipterus cyclophthalmus Kjellesvig-Waering, 1963.

Distribution.—Illinois and Czechoslovakia (?).

Stratigraphic range.—Middle Pennsylvanian (Illinois); Lower Carboniferous? (Czechoslovakia.)

Remarks.—There is a marked resemblance of this form to Laurieipterus and Ctenopterus, but the very different type of eyes precludes further comparison. It should be noted that in the holotype, the ventral shield had been reflected through, although preservation did not permit detailed description; it is important to record that the triangular transverse line, marking off the anterior rostral area from the inclined posterior part, as in Limulus, and in Brachyopterella, Laurieipterus, and other Stylonuracea as well, was discernible. It might therefore be rather safe to speculate that this genus retained an epistoma.

The genus comprises one species, with another doubtfully included:

Diagnosis.—Stylonuracea of medium size; outer surface covered with coarse scales and tubercles; prosoma campanulate, with stylonuroid appendages increasing in size posteriorly; first and second tergites greatly developed, the others normal in length.

Type genus.—Woodwardopterus Kjellesvig-Waering, 1959.

The family is considered to include two genera, Borchgrevinkium and Woodwardopterus.

Diagnosis.—Carapace elongated-parabolic; eyes unknown; legs mainly unknown, except basal (?) joints, which are highly spinous, undifferentiated; mesosoma with first two tergites longer than the rest of the mesosomal tergites; opisthosoma undifferentiated, with trilobation, caused by two ridges, present from the third to the tenth tergites; pretelson with dorsal forked area and telson short and