ISOPODS OF NORTH AMERICA. 



255 



cles of the first pair of antennae are widely separated, being nearly 

 2 mm. apart. The maxillipeds have a palp of two articles. The palp 

 of the mandibles is composed of three articles. 



The first segment of the thorax is about twice as long as any of the 

 three following segments, which are subequal. The antero-lateral 

 expansions of the first segment are half as wide as the head, 3 mm. in 

 width, and they are widely rounded at the anterior extremity. The 

 fifth and sixth segments are half as wide in the median longitudinal 

 line as any of the three preceding segments. The seventh segment is 

 a little shorter than the sixth. The epimera are distinctly separated 



FIG. 263. CYMOTHOA (ESTRUM (AFTER SCHICEDTE AND MEINERT). a, YOUNG OF THE SECOND STAGE 

 (ENLARGED), b, YOUNG OF THE FIRST STAGE (ENLARGED). C, LATERAL VIEW OF THORAX OF ADULT 

 FEMALE (REDUCED), d, ADULT MALE (ENLARGED). , ADULT FEMALE (REDUCED). /, ADULT FEMALE 

 (REDUCED). 



on all the segments with the exception of the first. They are narrow 

 plates, extending or nearly extending the full length of the segments. 

 Those of the second segment are a little broader anteriorly than are 

 the others. 



The abdomen is deeply set in the thorax. All the segments are dis- 

 tinct, the lateral parts of the first two being covered by the seventh 

 thoracic segment, so that these segments appear abruptly narrower 

 than the thorax. The following segments gradually increase in width. 

 The sixth or terminal segment is twice as broad as long, 6 mm. : 12 



