ISOPODS OF NORTH AMERICA. 



541 



Fig. 582.— Phyllodurus abdominalis. 

 Female (dorsal view). 



the last two segments the epimera occupy tlie post-lateral margin and 

 are not separated from the segment. 



The abdomen is composed of six distinct segnKMits. The first seg- 

 ment is provided on either side near the antero-lateral margin with a 

 papillose process. This segment is nearly 

 twice as long as an}" of the following seg- 

 ments. The segments of the ai)d()men 

 are successively narrower, gradually and 

 rapidly tapering to the sixth or terminal 

 segment which is produced posteriorly 

 in a long, narrow, tapering process. 



On either side of the lateral margins of 

 the tirst five abdominal segments are at- 

 tached two long, narrow processes, arising 

 from a connnon stem or peduncle. These 

 are probably the pleopoda, which may be 

 considered as double-branched. There 

 are thus ten of these on either side, or 

 twenty in all — i. e., live pairs of double- 

 branched pleopoda. On either side of the 



sixth or terminal segment the uropoda are attached. They are single- 

 l)ranched, each consisting of one long, narrow cylindrical process. 

 The ventral side of the last two thoracic segments is produced on 

 the posterior margins in keels. The ventral side of the abdominal 

 segments is slighth' keeled. 



There are five pairs of incubatory plates. The distal 

 part of the first lamella is posteriorly produced in a 

 triangulai'ly rounded lobe. 



The seven pairs of legs are prehensile in character; 

 the basis is not produced in a carina. 



The 5'oung female has one of the branches (the inner 



one) of the pleopoda very much shorter than the other 



branch. The head is not bilobed, and has the front more 



circular in outline. 1 have examined three adult females, 



two young females, and two males. The two young 



females had rudiments of the incubatory lamellae, the 



plates being larger in one specimen than in the other, 



and the inner branch of the pleopoda also larger. One 



specimen is a little older than the other. 



Most of the specimens were kindly sent to me by Doctor Caiman. 



They were sent to him from Columbia University, New York. Another 



specimen, a female, was sent to me later by Dr. William E. Ritter, of 



the University of California. 



Description of male. — Body oblong-ovate, a little more than twice as 

 long as wide, 2i mm. : 6 mm. 



Fig.583.-^Phyllo- 

 durvs abdomi- 

 NALIS. One of 

 BIBAMOUS PLE- 

 OPODS OF ADULT 

 FEMALE. X 7. 



