ISOPODS OF NORTH AMERICA. 



421 



wide but short, and extending to the end of the second article of the 

 peduncle of the second pair of antenna?; the second article is one and 

 a half times longer than the first article; the third article is three- 

 fourths as long as the second. The flagellum is composed of fourteen 

 articles, and extends to the end of the peduncle of the second pair of 

 antenna?. The second pair of antenna? have the first three articles 

 short and subequal; the fourth article is as long as the first three 

 taken together; the fifth is one and two-thirds times longer than the 

 fourth. The flagellum is composed of about ninety articles, and 

 extends to the posterior margin of the fifth thoracic segment, and is 

 10 mm. long. The maxillipeds have a palp of five articles. The palp 



of the mandibles is composed of 



three articles. 



The first segment of the thorax 



is slightly longer than any of the 



others, which are subequal, be- 



FIG. 472. ABELLTJS COMMUNIS (AFTER SMITH). 



FIG. 473. ASELLUS COMMUNIS. 

 O, FIRST LEG OP MALE. X 

 lli. 6, UROPOD. x Hi. 



ing each 1 mm. in length. The first segment is 1^ mm. long. All 

 the segments, including the first, have small epimera situated at the 

 antero-lateral angles of the segments. 



The abdomen is composed of two short segments, visible only in 

 the middle of the dorsal surface, and a large terminal segment, 5 mm. 

 wide and 4$ mm. long, with the post-lateral angles rounded and the 

 posterior margin produced in a broad triangular process between the 

 uropoda. The uropoda are about as long as the terminal abdominal 

 segment, being 4 mm. long. The peduncle is 2 mm. in length and is 

 1 mm. wide. The inner branch of the uropoda is broad and tapers to 

 a narrow, acute extremity. The outer branch is half as wide and is 

 about two-thirds the length of the inner branch; it is also produced 

 to a narrow and pointed extremity. In the female the first -pleopoda 

 are attached close together. 



The first pair of legs are prehensile and have the propodus greatly 

 expanded, and the inferior margin produced in one long and one short 

 triangular process. All the other legs are ambulatory. 



