New Species of Trilobite from the Trenton Limestone at Trenton Falls, N. Y.
New Species of Trilobite from the Trenton Limestone at Trenton Falls, N. Y. By C. D. Walcott.
R. striatulus, (n. sp.)
|Fig. 27. Remopleurides striatulus. a Anterior surface of hypostoma. b Ventral surface of hypostoma. The hypostoma figured is of the same size as that of the trilobite A.|
General form obovate, strongly convex. Head subrotund. Glabella prominent, central portion slightly convex, broadest at the posterior third, contracted at the base, where the width is the same as at the anterior margin of the eyes. A narrow palpebral lobe encircles the lateral margins two-thirds the length of the head. Anterior margin narrows and curves abruptly downward. Three pair of glabellar furrows are indicated by smooth lines; anterior and posterior very obscure. Neck segment narrow, well defined from the glabella by being slightly depressed; a minute tubercle occurs upon the anterior central third.
Movable cheeks; upper margin forms the base of the eye; anteriorly an acute angle terminating under the anterior base of the eye; posterior margin with two spines; the inner short, sharp pointed, curves downward and backward on a line with the pleura of the first segment of the thorax; outer spine long, nearly flat, obliquely striated, terminates opposite the axial lobe of the fifth segment.
At the anterior base of the eyes the outer margin of the movable checks curve abruptly downward and under forming a doublure, which extends around under the anterior margin of the glabella, and backward under the cheeks to a line with the neck segment.
Eyes large, elongated, depressed, occupy the curved space between the upper margins of the cheeks and the lateral margins of the glubella: perpendicular in hight to each, surface finely reticulated.
Facial sutures cutting the neck segment on a line with the base of the eyes, extend obliquely up to the posterior lateral angles of the glabella; curve outward around the top of the eyes, then abruptly down forming their anterior margin, curving forward and slightly upward they unite in front of the glabella.
Hypostoma; body quadrate, buccal margin produced into two long tapering lobes, with a deep buccal notch between them; upon the ventral surface four elevated lines run the length of each lobe, two central and one on each margin, the marginal lines of the outer margins continue to the anterior margin of the body, three short lines separating them near the anterior margin; muscular scars slightly elevated, oval, situated anterior to the buccal notch, they are crossed by minute inosculating lines. Interior or dorsal surface of the body cut away anteriorly forming a semi-circular depression, showing the interior of the ventral surface, and muscular scars as slight depressions crossed by minute striæ; ventral surface minutely tubercular, interior surface smooth. The hypostoma was attached to the doublure beneath the glabella; the extremities of the buccal lobes extending back to the anterior edge of the seventh thoracic segment.
Thorax with ten segments arching forward, narrows rapidly to the pygidium; axial lobe separated from the plural lobes, by a sharp ridge extending two-thirds the distance across each segment, a slight diagonal furrow crosses the segments of the axial lobe near the junction of the axial and plural lobes. Pluræ flat, curving down one-half the way outward where they are reflected backward, terminating in short pointed extremities.
Pygidium small, subquadrate, posterior margin narrowing is divided by a semi-circular depression into two short abruptly attenuate points, obliquely striated from the medial line backwards.
Surface. Glabella finely tuberculated. Movable cheeks very finely granulated. Axial lobe smooth with a few fine punctures. Outer spines of the head, pleuræ, (outer and inner surface), and pygidium striated.
Formation and locality. Upper third of the Trenton Limestone, Trenton Falls, N. Y. The glabella of this species closely resembles the glabella described by Prof. E. Billings as Remopleurides Canadensis, from the Chazy Limestone. Differs in the narrow palpebral lobes and glabellar furrows.
This work is in the public domain in the United States because it was published before January 1, 1928.
The longest-living author of this work died in 1927, so this work is in the public domain in countries and areas where the copyright term is the author's life plus 95 years or less. This work may be in the public domain in countries and areas with longer native copyright terms that apply the rule of the shorter term to foreign works.