species to Stylonurus. The presence of this genus, or rather of that branch of the eurypterids which leads to the late Siluric and Devonic Stylonurus, is further indicated by body segments (tergites) [pl. 85, fig. 6] which have the form and ornamentation of the Otisville species Stylonurus myops.
Description. Carapace elongate semielliptic, a little longer than wide, widest at the base and contracting uniformly to the front which is evenly rounded. The posterior margin is straight transverse. The carapace is surrounded on all sides by a distinct border which is broadest in front where it attains one eighth the length of the carapace, and narrowest along the posterior margin. On the upperside this border slopes outward and is smooth, on the underside it was flat and concentrically grooved. The eye nodes are large, about one fifth the length of the body, circular, situated just in front of the transverse middle line of the carapace, close-set, about their own diameter apart. The visual surface has not been clearly distinguished from the node and it may have occupied the entire node. The ocelli have not been seen. The ornamentation is not visible on the carapace, but tergites probably belonging to the same species show circular to elliptic, relatively large nodes.
The tergites are strongly curved, convex forward in the middle and concave toward the sides, with very prominent "ears" at the antelateral angles and much rounded postlateral angles. They were very convex in the middle and surrounded by a depressed border.
Long slender tubular leg segments [pl. 85, fig. 9] and broad flat leg spines also occur in the Frankfort shale, such as among the later eurypterids are only known from the Stylonurus group.
Horizon and localities. Frankfort shale (Schenectady facies) at Schenectady and Duanesburg.
Remarks. Besides these elongate carapaces, a broad short carapace with the eyes far apart has been found at Schenectady [pl. 85, fig. 4]. This closely resembles the S. myops from Otisville. Like the latter, it has a very broad, concentrically striated or grooved border. This cara-
