. Bulletin - United States National Museum. Science. ISOPODS OF NORTH AMERICA. 415 which is 4 mm. in length and has the posterior margin widely rounded. The terminal segment is 5 mm. wide at the base. The uropoda are half as long as the terminal abdominal segment. The peduncle is 1 mm. long. The outer branch is 1 mm. long. The inner branch is a very little longer than the outer branch. In the female the first ple- o})oda are attached close together as in the preceding species. The first pair of legs are strongly prehensile and have the propodus greatl}' dilated and the inferior margin armed wi
. Bulletin - United States National Museum. Science. ISOPODS OF NORTH AMERICA. 415 which is 4 mm. in length and has the posterior margin widely rounded. The terminal segment is 5 mm. wide at the base. The uropoda are half as long as the terminal abdominal segment. The peduncle is 1 mm. long. The outer branch is 1 mm. long. The inner branch is a very little longer than the outer branch. In the female the first ple- o})oda are attached close together as in the preceding species. The first pair of legs are strongly prehensile and have the propodus greatl}' dilated and the inferior margin armed with two triangular processes. All the other legs are ambulatory. MANCASELLUS TENAX (Smith). Asellus tenax Smith, Ainer. Jour. Science and Arts, (3), II, 1871, pp. 453-454. Asdlojisis U'liax', Anier. Jour. Science and Arts, (3), VII, 1874, p. 601; Harger in Smith, Report U. S. Commissioner of Fish and Fisheries, 1874, pp. 659-660, pi. I, fig. 3. Mancaselhis tenax Harger, Amer. Jour. Science and Arts, (3), XI, 1876, p. 304.— Hay, Amer. Nat., XVI, 1882, p. 242.—Underwood, Bull. 111. State Lab. Nat. Hist., II, 1886, p. 359.—Richardson, American Naturalist, XXXIV, 1900, p. 297. Localities.—Lake Superior; Indiana; Michigan; Lake Huron. Bod}' oblong-ovate, a little more than two and a half times longer than wide, 3 mm. : 8 mm. Head twice as wide as long, 1 mm. : -1 mm., with the anterior mar- gin excavate on either side of a small median point. Lateral margins somewhat expanded in an anterior and a posterior lobe, the posterior lobe being produced laterally much beyond the anterior lobe. Between the anterior and the posterior lobe the lateral margin is slightly exca- vate. The eyes are small, round, composite, and situated opposite the excavation a short distance from the lateral margin. The tirst pair of have the tirst arti- cle large and dilated; the second article is half as wide as the tirst article and twice as long; the third article is less than half the
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