330 © GEOLOGICAL SURVEY 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 Polyartemia of Dr. 8S. Fischer* is re- 
markable for possessing 19 pairs of feet; the tail is short, the ovisae 
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. Polyartemia 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 Verrill. 
Plates VIII, XXII, figs. 1, 2, 2a, 2b; XXIII. 
Artemia gracilis Verrill, Amer. Journ. Sc. 2d Ser. xlviii, 248, Sept. 1869. Proc. Amer. 
Assoc. Adv. Se. July, 1870. 
Artemia monica Verrill, Amer. Journ. Se. 2d Ser. xlviii, 249, Sept. 1869. Proc. Amer. 
Assoc. Adv. Se. July, 1870. 
Artemia fertilis Verrill, Amer. Journ. Sc. xviii, p. 430, Nov. 1869. Proc. Amer. Assoc. 
Ady. Se. 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, the 
2d joint varying with age and 
in different individuals from the 
“i Same locality; it is unusually 
aa broadly triangular and from 
Fic. 17. Artemia gracilis, from Great Salt Taba A pair one-half to two-thirds as wide 
swimming, the male clasping its mate with the claspersaS long; at the outer angle is 
(0) infront ofthe ovicgo (c): elatgedahontZtines. Als a large angular projection, while 
(e) still more enlarged. Emerton del. the apex is acutely pointed and 
slightly excurved (Pl. VIII, fig. 1). The frontal knobs on the inside of 
the Ist or basal joint are small, rounded, button-like. The ocellus is 
black, trilobate. Thelegsare long and slender; the 6th endite narrow, 
long, and acutely triangular; the 5th endites full and rounded. The 
abdomen is slender, and the cercopoda very short, usually scarcely as 
long as one-half the width of the terminal segment of the abdomen. 
In color either whitish, flesh-colored, often deep red, sometimes green- 
ish, with black eyes. 
Length of male, 8-10™™ ; female, 10-12™™, 
For the reasons stated beyond I am disposed to unite Verrill’s A. mo- 
nica and A. fertilis with his first described form, A. gracilis, as I do not 
regard the difference he points out as more than individual; probably 
* Middendorf’s Sibirische Reise, Bd. II, Thl. 1, 154, 1851. 
+From Great Salt Lake, with a brief description. 
