Page:The Eurypterida of New York Volume 1.pdf/224

 for this reason be unwarranted to unite it with the latter subgenus, especially since both lived under unlike abnormal marine conditions, that is, Tylopterus in very saline water, Anthraconectes in brackish or fresh water.

Whiteaves. Paleozoic Fossils, v. 3, pt 1. 1884. p. 42. pl. 7. fig. 3

The species was very carefully described by Whiteaves as follows:

Carapace moderately convex, broader than long, greatest breadth a little above the middle; semiovate, broadly rounded in front and squarely truncated behind; sides somewhat convex at their margin above, but straighter below; front and sides bordered by an elevated, narrow ridge, which is highest and most strongly marked on the posterior half of the sides. Eyes reniform, prominent, about 4 mm in the greatest diameter; 9 mm apart (as measured from the center of their inner margins) and placed at a distance of 6 mm from the anterior, and of 7 mm from the lateral margin. Ocelli not clearly indicated, but probably placed on or near a small rounded prominence or elevation, which is situated exactly in the middle of the space between the two eyes. Surface of the carapace apparently finely granulose, and ornamented with minute rounded tubercles, some of which are isolated and others confluent in sets of two or three.

Thoracic and caudal portions together consisting of 12 segments, exclusive of the telson or caudal spine; the first, second, third and fourth thoracic segment each bearing on the median line a single, large and prominent, transversely elongated tubercle, which is arcuate or reniform at its base and somewhat bilobate at its summit. The lateral diameter of each of these tubercles greatly exceeds the longitudinal, and measuring at their base, the proportions of each tubercle may be thus approximately estimated; that on the first thoracic segment, lat. diam. 4 mm, long diam. not quite 1 mm; that on the third, lat. diam. nearly 5 mm, long diam. rather more than 1 mm; that on the third, lat. diam. 5 mm, long. diam., 2 mm; and that on the fourth, lat. diam. 5½ mm, long diam., 3 mm.

Telson produced into a gradually narrowing, slightly curved, and rather obtusely pointed linear spine, which seems to be triangular in transverse section.

Antennae, endognaths and ectognaths unknown, as is also the nature of the surface markings of the test of the thoracic and caudal segments.

Entire length, including the telson, about 75 mm (or 3 in.); length of carapace, 20 mm, greatest breadth of the same, 27 mm; length of telson, 15 mm.