ISOPODS OF NORTH AMERICA. 



289 



^e^ 



articles. The tirst antenna' extend to the posterior margin of the 



head. The second antennjs have the first two articles very short and 



eqnal in length; the thii-d and fourth are al)out equal in length and 



each is twice as long- as the second; the fifth article is one and a half 



times longer than the fourth. The flagellum is 



composed of nine articles. The second anteniue 



extend almost to the posterior margin of tiie tirst 



thoracic segment. The maxilliped has a palp of 



five articles. The niaiidi))le has a pal}) of three 



articles. 



The tirst segment of the thorax is a little longei' 

 than any of the others. The lateral parts of all 

 the segments are bent downward, forming an 

 angle with the dorsal ])()i-tion. The epimora ai'c 

 not distinct from the segments, but are indicated 

 b}^ a faint line on either side of the segment 

 a little distance within the place where the 

 lateral part of the segment forms the angle with the dorsal ]^art. 



The abdomen is com^wsed of two segments. The tirst segment has 

 three suture lines on either side, indicating three coalesced segments. 

 The terminal segment is triangulai- in shape with apex rounded. The 

 ui-opoda are very large, both branches extending to the tip of the 

 abdomen, and being of ecpial width. The outer moval)le branch is 



Vu:. :m.— ExosPH.KRoMA 



A M ri.l (• A ID A (AFTEK 

 STIMI'SON). X s. 



Fui. 802.— K.\()s1'U.i:koma AMri.icAi'DA. 0, /), Mani)Ibi,k.s. -,51^. c, Ma.vh.lu'ED. x51|. (/, Kkontai. 



LAMINA AND CLYPEUS. 5]|. 



rounded posteriorly. The inner innnoval)le branch has the outer post- 

 lateral angle rounded, the imier one produced. 



The last three segments of the thorax and the tirst seguuMit of the 

 abdomen have rudiments of tubercles on their posterior margins. 

 In the specimens examined there are no tubercles on the anterior seg- 

 ments, which may be due to size, all the specimens })eing viuy small. 

 There are also four tiny tubercles arranged in two longitudinal series 

 of two, one on each side of the median line at the base of the terminal 

 segment. The legs are all ambulatory. 

 28589—05 19 



