Page:The Eurypterida of New York Volume 1.pdf/264



Nine carapaces which have in common the broad, short, subtriangular form and the forward position of the marginal lateral eyes, bear a close resemblance to the carapace of  from the Bertie waterlime. The largest of these [pl. 84, fig. 7], which is also the most distinct, has been selected as the type of the species.

Description. Carapace broadly subtriangular in outline, twice as broad as long (length of type, 20 mm, width, 43 mm), the lateral margins gently convex in the anterior third, forming a blunt frontal angle. Posterior margin straight transverse or broadly convex forward; genal angles acute. The lateral eyes are marginal, situated one third of the length of the lateral margin from the frontal apex, small (one seventh to one eighth the length of the side), bean-shaped, the visual surface apparently occupying the entire node. No facets seen. Ocelli situated in the middle of the carapace.

In several specimens the first tergite is found attached to the carapace. This is broad and short, about seven times as wide as long. In another specimen [pl. 84, fig. 9] the preabdomen and the proximal portion of a swimming leg are also preserved.

The carapace and first tergite were smooth or have only small, scattered tubercles.

Horizon and localities. The Frankfort shale (Schenectady beds) at Schenectady (Dettbarn quarry), Duanesburg and Rotterdam Junction.

Hall erected Dolichopterus as a subgenus of Eurypterus, citing as its distinguishing characters: the development of the "palette" (ninth segment), the less dilatation of the natatory feet, the form of the metastoma, and of the "central footlike organ" (genital appendage). It has been accorded full generic rank by later authors, with perfect propriety, we feel