ISOPODS OF NORTH AMERICA. 



675 



The first and second articles of the second pair of antennae are sub- 

 equal; the third article is one and a half times longer than the second; 

 the fourth is twice the length of the third; the fifth is one and a half 

 times longer than the fourth. The flagellum is composed of twenty- 

 eight articles. When retracted, 

 the second pair of antennae extend 

 to the end of the fifth abdominal 

 segment. The maxilliped has a 

 palp of five articles. 



The first five segments of the 

 thorax are about equal in length; 

 the last two are somewhat shorter. 

 The posterior angles of the lat- 

 eral parts of the last three are 

 produced downward. The lateral 

 parts of the segments are not sep- 

 arated oft' from the dorsal portion. 



FIG. 714. LlGYDA OLFERSII. a, MAXILLIPED. 



x 20i. b, FIRST LEG OF MALE, x Hi. 



FIG. 715. LlGYDA OLFERSII. X 3. 



There is not even any trace, such as a faint line, to mark the place 

 where coalescence has taken place. 



The abdomen is as wide as the thorax, the lateral parts of the 

 third segment extending as far as those of the seventh thoracic seg- 

 ment. The lateral parts of the first two segments are not developed. 

 There is a slight and gradual increase in the length of the segments 

 from the first to the fifth. The lateral parts of the abdominal seg- 

 ments are not separated off from the dorsal portion. The middle 

 portion of the sixth or terminal segment is produced triangularly 

 in an acute point. The lateral angles are short and acute, and do not 

 extend to the tip of the median point. Between the lateral parts 

 and the dorsal portion, there are two angular processes on the poste- 

 rior margin of the segment, on either side, near the lateral angles, 

 the process adjacent to the lateral angle being more obtuse than the 

 other one. 



