Page:A Revision of the Families and Genera of the Stylonuracea (Eurypterida).djvu/23

and with sides nearly parallel; male operculum unknown; female operculum short, composed of one undivided joint with slightly rounded margins that comprises most of the appendage, and a short triangular termination that is divided into two parts, each of which forms a narrow triangular prong (see fig. 97); telson very narrow, spike-like, forming a conspicuous attenuation in comparison to the metasoma; ornamentation consists of fine to coarse scales and mucrones.

Type species.—Stylonurus (Drepanopterus) longicaudatus Clarke and Ruedemann, 1912.

Derivation of name.—Named from the area of Kokomo, Indiana which has furnished the famous Kokomo eurypterid fauna.

Distribution.—Indiana.

Stratigraphic range.—Upper Silurian.

Remarks.—The genus Kokomopterus differs from Drepanopterus in having a subquadrate carapace with anteriorly located eyes as against a horseshoe shaped carapace with eyes located at midsection. The opisthosoma of Kokomopterus has a clearly differentiated preabdomen as contrasted with the opisthosoma of Drepanopterus, which

Fig. 97. Female (Type B) operculum of Kokomopterus longicaudatus (Clarke and Ruedemann) from the Silurian Kokomo dolomite of Kokomo, Indiana. The mid-line represents the transverse suture. There were no deltoid plates developed. The inner part of the opercular plates and the median organ were covered with setae.