ISOPODS OF NORTH AMERICA. 



103 



a little shorter than the first; the third is equal in length to the first two 

 taken together. The flagellum is composed of twelve articles. The 

 first antenntv extend to the end of the fourth article of the peduncle 

 of the second antennae The first two articles of the second pair of 

 antenntv are short; the second is shorter than the first; the third and 

 fourth articles are about equal in length and each is as long- as the first 

 two taken together; the fifth article is one and a half times longer than 

 the fourth. The fiagellum is composed of twent3'-four articles. The 

 second antenna? extend to the posterior margin of the second thoracic 

 segment. The maxilliped is composed of seven articles. The palp of 

 the mandible is composed of three articles. The frontal lamina is nar- 

 row and elongate, with the anterior end rounded and more flattened 

 than the posterior end, which is attenuated. 



The first segment of the thorax is longer than any of those follow- 

 ing. The seventh segment is shorter than any of the others. The 



Fig. 84.— Cirolana borealis. a, Maxilliped. x 27j. 6, Mandible, x 2"j. c, Second maxilla. 

 X 27^ d, Frontal lamina, x 51|. 



epimera are distinct on all the segments with the exception of the first. 

 They are broad plates, the last four being wider than the first two 

 and crossed obliquely b}^ a carina. The outer post-lateral angles of 

 the last three are produced beyond the posterior margin of the seg- 

 ment and are more acute than in the first three. 



The first segment of the abdomen is partly concealed bv the last 

 thoracic segment. The sixth or terminal segment becomes narrower 

 to a rounded extremit}^ which is crenulate and furnished with ten 

 spines. The inner branch of the uropoda is wide and extends some- 

 what beyond the extremity of the last abdominal segment. Its outer 

 post-lateral angle is slightly produced. The outer branch is half as 

 wide as the inner branch, is a little shorter, and is produced to a 

 pointed extremit}'. The margins of both branches are crenulate and 

 armed with spines. The peduncle extends about two-thirds the length 

 of the terminal abdominal segment. 



