ISOPODS OF NORTH AMERICA. 



301 



Body narrow, linear, rtliforni, at)()ut four times lonj^er than wide, 

 4 mm.: IT mm.; leii<>tli of abdomen about one-third that of entire 

 length of l)ody, G nun.: IT nun. 



Head wider than long, with anterior margin .slightly excavate. 

 Anterior portion of head hut slightly wider than posterior portion. 



Fig. 389.— Idothea rectilinea. 



Fig. 390.— Idothea kectiunea. a, Maxili.iped. x 23. 

 ■ 6, First antenna, x 23. 



E\'es ver}^ small, transversely ovate, compound in structure, and situ- 

 ated about the middle of the extreme lateral margin. First pair of 

 antenna^ with the basal article enlarged; second and third articles 

 equal in length, and somewhat shorter than the basal joint; fourth 

 article clavate and a little longer than either of the two pi-eceding 

 ones. The first antennae extend to the middle of the third peduncular 

 article of the second pairof antenna\ The basal article 

 of the second antenniv is scarcely visi])le from a doi'sal 

 view; the second and third articles ai'C of equal length: 

 the foui-th and fifth are subequal and each is about twice 

 as long as the third. The Hagellum is composed of 

 thirteen long, slender articles. When reti'acted, the 

 second antemnv extend to the posterior margin of the 

 fourth thoracic segment. The maxilliped has a palp of 

 four articles. 



The segments of the thorax are about equal in length, 

 the tirst one only being a little shorter than the others. 

 The tirst segment is not wider than the head. The epimera of the 

 second, third, and fourth segments occupy the anterior half of the seg- 

 ments, and are very narrow; the epimeron of the fifth segment occupies 

 the anterior two-thirds part of the segment; the epimera of the last 

 two segments occupy the entire lateral margin. 



Fl(i. 391.- lUOTHEA 

 RECTILINEA. .\B- 

 DOMEN. X (>s. 



