PACKARD.] PHYLLOPODS OF NORTH AMERICA. 329 



Abdomen with nine segments ; male claspers simple, cylindrical ; ovisac 



long, slender Branchinecta 



b. Frontal appendages present. 

 Frontal appendages ribbon-like, or broad triangular 5 2d joint of male 



claspers chitinous, simple, bent at tip Branchipus 



Second joint of male claspers long, tortuous, and forked irregularly; 



ovisac long and slender. Streptocephalus 



Frontal appendages long and variously lobed or spinulose ; ovisac short 



and broad Chirocephalus 



Genus AETEMIA Leach. 



Plates VIII, XXII, XXIII. 



Cancer Linnaeus, Systema Nat. ed. 12, i, pars. 2, 1058. 



Apus Schaeffer, Monogr. fig. 1, 12, 1754. 



JBrancMopoda Lamarck, System, des Auim. sans vert. 161. 1801. 



Branchiopoda Latreille, Gen. Crnst. et Insect, i, 22, 1806. 



Eidimme Latreille (pre-occiipied), * 1817. 



Artemia Leach, Diet, des Sc. Nat. xiv; 1819. 



Body very slender, with eleven pairs of feet; the head rather smaller 

 in proportion than in the other genera of the family ; the male claspers 

 (2d antennse) very large, thin, and broad; 2-jointed, the 2d joint bent 

 at nearly right angles upon the 1st, the latter thick, about twice as long 

 as thick, a deep rounded sinus between the bases of the claspers ex- 

 actlj^ fitted so as during connection with the female to enclose her back. 

 Near the middle, on the inner side of the 1st joint, a knob-like projection. 

 The 2d joint simi)le, broad, flat, acutely triangular, from J to f as broad 

 as long. The legs beyond the 5th eiidite rather slenderer and more 

 pointed than in the other genera. The gill is moderately large, about 

 half as wide as long ; the flabellum broad and rounded, the edge serrate 

 and setose as usual. The 1st endite divided into two lobes, the 2d of 

 which is about ^- as long as the 1st; endites 2-4 are minute, conical; 

 the 5th is moderately large and rounded on the outer angle, with large, 

 coarse setae, the distal edge oblique and somewhat full and rounded ; 

 the Cth is narrow, long, and more ])roduced and acutely pointed than 

 usual, much more so than in Branchinecta or any other genus of the 

 family, while the setae are much longer than in Branchinecta. 



Abdomen eight-jointed, very slender, ending in a pair of unusually 

 short, small cercopods (caudal api)endages) not more than twice as long as 

 broad, being less than half as long as in Branchinecta, and less than half 

 as long as the terminal segment. The male genital deeply cleft, each 

 half long and slender, more so than in Branchipus, but somewhat as in 

 Branchinecta, though shorter and less curved. Ovisac of the female 

 rudely bottle shaped, shorter and broader than in any of the other 

 genera, with a short, broad "neck" or opening. 



Eemarls. — This genus is in some respects simpler than Branchinecta, 

 or any other genus of the family, and differs decidedly from any other 

 genus, not only in the small size of the body, but also in the broad, flat, 

 triangular 2d joint of the male claspers, as well as in the much smaller, 

 shorter caudal appendages, and the long, narrow, acute distal or 6th 

 endites, which render the legs rather long and slender. The ovisac is 

 also shorter and broader than usual. 



*Accordiug to Dr. Baird (Monograph of the Family Branchipodidse, etc., in Annals 

 and Mag. Nat. History, siv, 216, 1854) the genus Eulimine Latreille, 1817, was based 

 on specimens of A. saliva, which were badly preserved and erroneously described. 

 That name was, however, pre-occupied among Acalephs, see Verrill, Observations, etc. 



