330 GEOLOGICAL SUEVEY OF THE TEERITORIES. 



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 ill Brancliinecta. Considering the fresh- water forms by them- 

 selves, Brancldnecta 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 BrancMnecta, and is a depaux^er- 

 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 BrancMnecta as the simpler form, affording us a truer stand- 

 ard of comparison than the less normal Artemia. 



The Siberiau fresh-water genus Polyartemia of Dr. S. Fischer* is re- 

 markable for possessing 19 pairs of feet ; the tail is short, the ovisac 

 quite volumiuoas ; 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 Middeudorf in pools on the Tundra, near the rivers Taimyr and Bo- 

 ganida, and also in Lapland, near the Tri-Ostrowa. 



Aetemia gracilis Verrill. 



Plates VIII, XXII, figs. 1, 2, 2a, 21 ; XXIIL 



Artemia gracilis Verrill, Amer. Journ. Sc. 2d Ser. xlviii, 248, Sept. 1869. Proc, Amer. 



Assoc. Adv. Sc. July, 1870. 

 Artemia monica Verrill, Amer. Journ. 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, Marcli, 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 

 same locality; it is unusuallj'" 

 broadly triangular and from 

 r. .c-..-r-, A • one-half to two-thirds as wide 



Fig. 17. Artemia gracilis, from Great Salt Lake. A pair - , ^i , ■ „ 



swimmins, the male clasping its mate with the claspers aS JOUg ; at tUe OUtCr aUgJC IS 

 (OJnfront of the ovisac (e) ; enlarged about 3 times. Also alargC angularproieCtiOU, while 

 a view from beneath of the male claspers (c) and the ovisac o p ^ , "^ • ^ i i 



(e) still more enlarged. Emerton del. the apeX IS aCUtely pOlUtCd and 



slightly excurved (PL- VIII, fig. 1). The frontal knobs on the inside of 

 the 1st or basal joint are small, rounded, button-like. The ocellus is 

 black, trilobate. The legs are long- and slender; the 6th endite narrow, 

 long, and acutely triangular; the 5th eudites 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 Yerrill'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 



" * Middeudorf 's Sibiiisclie Reise, Bd. II, Tbl. 1, 154, 1851. 



tFrom Great Salt Lake, with a brief description. 



