ISOPODS OF NORTH AMERICA. 



677 



FIG. 717. LIGYDA EX- 

 OTICA. MAXILLIPED. 

 x 15}. 



second pair of antennae. The first and second articles of the second 

 pair of antenna 1 are about equal in length; the third article is about 

 one and a half times longer than the second; the fourth is three times 

 longer than the third; the fifth is one and a half times longer than 

 the fourth. The flagellum is composed of fifty -five 

 articles. When retracted, the second antenna? ex- 

 tend to the end, or a little beyond the end, of the 

 peduncle or basal article of the uropoda. The max- 

 illipeds have a palp of five articles. 



The segments of the thorax are subequal. The 

 epimera are broad plates occupying the entire lat- 

 eral margins of the segments, but not distinctly 

 separated off from the dorsal portion of the seg- 

 ment, only a faint line, almost inconspicuous, indi- 

 cates the place where the coalescence has taken 

 place. The lateral parts of the last three segments 

 extend downward. 



The abdomen is not narrower than the thorax, 

 the third segment being as wide as the seventh thoracic segment. The 

 lateral parts of the first two segments are not developed. There is a 



gradual increase in the length of the seg- 

 ments from the first to the fifth. The 

 lateral parts of the third, fourth, and fifth 

 segments are not distinct from the dorsal 

 portion of the segment. The sixth or ter- 

 minal segment has the middle part of the 

 posterior extremity produced triangularly 

 in an obtuse point. The post-lateral angles 

 are very acute and long, extending as far 

 as the apex of the middle portion. Be- 

 tween the lateral angles and the middle 

 portion of the segment, but near the lat- 

 eral angle, are two small triangular pro- 

 cesses. The basal article of the uropoda 

 is 6 mm. in length from the apex of the 

 terminal abdominal segment. The 

 branches are of equal Jength and twice 

 as long as the peduncle, being 12 mm. 

 The inner branch is furnished with a small 

 bristle about half a mm. long. 

 The legs are all ambulatory. In the male the first pair has the pro- 

 podus furnished near its distal end with a small lateral process. This 

 process is wanting on the first pair of legs in the female. 



FIG. 718. LIGYDA EXOTICA, a, TER- 

 MINAL JOINTS OF FIRST LEG. X 11|. 



6, FIRST LEG. x llj. 



