ISOPODS OF NORTH AMERICA. 



245 



each being 2 mm. lono-. The fourth uiid tit'th are .su})equal, each being 

 1 mm. in UMigth. Tiie sixth and scxcntii are each only ^ mm. long. 

 The epimiM'a are not distinctly separated on th(» tirst segment. The 

 following tive segments ha\'e distinct epimera. There are none on the 

 seventh segment, and there are no appendages to this segment. There 

 are two paii-s of legs attached to the fourth segment, two legs on 

 either side, and two pairs of epimera. The epimera of the second and 

 third segments are narrow plates, extending the full length of the 

 lateral margin on the shortened side of the body, the epimera of the 

 third segment on the longer side not extending quite to the post-lateral 

 angle. The fourth segment has two pairs of epimera, an anterior and 

 a posterior pair; the two are equal in size on the short side, the ante- 

 rior one on the long side of the bod}- being small, the posterior one 

 being transversely elongated, not laterally placed, })ut extending along 

 the posterior margin of the lateral expansion of the segment. The 

 epimera of the tifth and sixth segments, on the short side of the body, 

 occupy the post-lateral angles; those of the long side are transversely 



Fig. 254.— Agarna carinata. a, Maxilliped. ■: 29. t>. Second maxilla, x 29. 

 iLLA. X 29. d, Mandible, x 29. c, Palp of mandible, x 29. 



c, First max- 



elongated, not laterally, but posteriorly placed on the lateral expan- 

 sions of the segments. There are no epimera on the seventh segment. 



The abdomen is deeply set in the thorax, the seventh thoracic seg- 

 ment covering the lateral parts of the tirst two or three segments. 

 The tirst segment of the abdomen is as wide as the last thoracic seg- 

 ment; the following segments gradually increase in width, especially 

 on the shorter side of the body, so that the abdomen here becomes 

 wider than the thorax. The terminal segment is large, triangular in 

 shape, with apex rounded; it is 6 mm. long and 8 mm. wide at the 

 base. The uropoda are very short, extending less than one-third the 

 length of the a])domen. The outer l)ranch is a little longer and wider 

 than the inner branch. 



The legs are all prehensile, Avith short, stout, curved dactyli. The 

 ischium of the last four pairs is flattened and very much longer than 

 in the first three pairs. There is also a moderately high carina on the 

 basis of the last four pairs of legs.* 



«For complete description of this form, the male and female and the young of the 

 first stage, see Schicedte and. INIeinert, Nat. Tidsskr., (3) XIV, 1883-84, pp. 329-334. 



