I8OPODS OF NORTH AMERICA. 81 



Family V. CIROLANID^. 



Body more or less semicylindrical in form. Epimera well defined 

 on all the segments of the thorax, with the exception of the first. 

 Abdomen usually composed of six distinct segments. Uropoda lateral, 

 and forming, with the last segment of the abdomen, a caudal fan. 

 Eyes usually small, lateral. Antennas usually unequal in length, 

 multiartlculate, with well-defined peduncle and flagellurn. -First three 

 pairs of legs usually prehensile; last four pairs ambulatory. Pleopods 

 well developed and adapted for swimming and breathing. Second 

 pair of pleopods in the male with a stylet inside the inner plate. 

 Incubatory pouch composed of five pairs of plates issuing from the 

 bases of the first five pairs of legs. 



Labrum large, two or three times wider than long. 



Clypeus large, wide, short, triangular. 



Mandibles wide throughout their entire length; the posterior part 

 seen in position turned a little inward; the distal part directed inward, 

 wide, but long, and covered for the most part; cutting part long, more 

 or less trifid, the posterior apex always larger than the other apices; the 

 movable lacinia is large, furnished with many spines; the molar part 

 is elongate, triangular, furnished with triangular processes on the 

 anterior margin. 



The first pair of maxillae are robust: the lacinia of the first article 

 is inflated at the apex and furnished with three plumose processes; 

 the lacinia of the third article is wide or very wide at the apex and 

 is furnished with many robust spines. 



The second maxillse are well developed; the lacinia of the second 

 article is wide, free, and short, and furnished with many setae;' the 

 lacinise of the third and fourth articles are much longer than wide, 

 with the inner margin furnished with long setse. 



The maxillipeds are well developed; the margins of the articles of 

 the palp are furnished with many setse, but never furnished with hooks. 



ANALYTICAL KEY TO THE GENERA OF THE FAMILY CIROLANID.E. 



a. All six segments of abdomen distinct, not coalesced. 



b. No branchiae developed at base of pleopoda. Eyes, when present, placed on 



superior and inferior side of head. 



c. Peduncle of the second pair of antennae composed of five articles. Plate of 

 the second joint of the maxillipeds furnished with hooks. First pair of 

 antennae with basal article of peduncle not placed at right angles to second 

 article. 



d. First three pairs of legs prehensile. Last four pairs ambulatory. Uropoda 

 with the inner angle of the peduncle produced. 



See Sars, Crust, of Norway, II, 1899, pp. 67-68, for characters of 

 Hansen, Vidensk. Selsk. Skr. (6), V, 1890, pp. 310-311, 317, 318. 

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