. Annual report. 1st-12th, 1867-1878. Geology. 330 GEOLOGICAL SUEVEY OF THE TERRITORIES. Compared with the other genera, this upon the whole stands at the base of the family, though the male claspers are a little more compli- cated than in Branchinecta. Considering the fresh-water forms by them- selves, Branchinecta is, without much doubt, the lowest or simplest in structure. As seems most probable from the experiments of Schman- kevitch, Artemia is a modification of Branchinecta., and is a depauper- ated form, smaller in size, with less developed caudal appendages, due to perhaps less favorab
. Annual report. 1st-12th, 1867-1878. Geology. 330 GEOLOGICAL SUEVEY OF THE TERRITORIES. Compared with the other genera, this upon the whole stands at the base of the family, though the male claspers are a little more compli- cated than in Branchinecta. Considering the fresh-water forms by them- selves, Branchinecta is, without much doubt, the lowest or simplest in structure. As seems most probable from the experiments of Schman- kevitch, Artemia is a modification of Branchinecta., and is a depauper- ated form, smaller in size, with less developed caudal appendages, due to perhaps less favorable means of obtaining food in its brine than the fresh-water forms. Hereafter, then, in diagnosing the other genera we will take Branchinecta as the simpler form, affording us a truer stand- ard of comparison than the less normal Artemia. The Siberian fresh-water genus Poly artemia of Dr. S. Fischer* is re- markable for possessing 19 pairs of feet; the tail is short, the ovisac quite voluminous; the male claspers are broad, flat, and consist of two branches, one covering the other ; the front of the head is prolonged into a broad, very thin tentacle-like organ; in other respects it agrees with the genus Branchipus. Poly artemia forcipata Fischer was found by Middendorf in pools on the Tundra, near the rivers Taimyr and Bo- ganida, and also in Lapland, near the Tri-Ostrowa. Artemia gracilis Yerrill. Plates VIII, XXII, figs. 1, 2, 2a, 21; XXIII. Artemia gracilis Verrill, Amer. Journ. Sc. 2d Ser. xlviii, 248, Sept. 1869. Proc. Amer. Assoc. Adv. Sc. July, 1870. Artemia monica Verrill, Amer. Jourri. Sc. 2d Ser. xlviii, 249, Sept. 1869. Proc. Amer. Assoc. Adv. Sc. July, 1870. Artemia fertilis Verrill, Amer. Journ. Sc. xlviii, p. 430, Nov. 1869. Proc. Amer. Assoc. Adv. Sc. July, 1870. Artemia utahensis Lockington,t Month. Micr. Journ. 137, March, 1876. This species is characterized by the slender body, its small head and small eye-stalks and eyes. The male claspers are rather slender,
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