Page:AmJourSci 3 23 135 213-216.djvu/1

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213
C. D. Walcott—New Genus of the Eurypterida.

Art. XIX.—Description of a New Genus of the Order Eurypterida from the Utica Slate; by C. D. Walcott.

In the February number of this Journal,[1] notice was given of the discovery of the fragmentary remains of a large Pœcilopod in the Utica slate and its identification with the Eurypterida, a provisional reference being made to the genus Eurypterus. A review of this and the genera of its order shows that none of them present the characters seen in the remarkable cephalic appendage from which the genus now proposed derives its name.

Echinognathus, n. g.

Endognathary limbs (one or more pairs) formed of eight or nine joints, six of which carry long, backward curving spines articulated to their posterior side. Terminal joint slender, elongate, acuminate. Surface of the body and larger joints of the cephalic appendage ornamented with scale-like markings, as in the genus Pterygotus. Type, E. Clevelandi.

Echinognathus Clevelandi.

Syn. Eurypterus? Clevelandi Walcott. This Journal, vol. xxiii, p. 151, 1882.

The only portion of the body discovered is illustrated by fig. 1. It appears to be the left side or half of the ventral surface of the anterior thoracic segment. The reference to the ventral surface is from the presence of a thin membranous

AmJourSci 3 23 135 213 figure 1.jpg

Fig. 1.—Reduced to 7-10ths the natural size.

extension of the anterior margin, a feature observed on the anterior segment of Dolichopterus macrocheirus Hall.[2] The test appears to have been thin and firm, and the margins are clearly outlined on the dark, smooth slate, while the surface is ornamented with fine scale-like markings on the anterior portion that increase in size toward the posterior margin (c c).

  1. Vol. xxiii, p. 151, 1882.
  2. Pal. New York, iii, p. 414*.