ISOPODS OF NORTH AMERICA. 



149 



to the first two taken together; the fourth and fifth are su))e(jual and 

 each is nearly twice as long as the thii'd. The Hao-ellmn is composed of 

 thirty-two articles. The s(>cond pair of antenna* extend to the poste- 

 rior margin of the third thoracic segment. The maxilliped is com- 

 posed of seven articles. The palp of the mandibles is composed of 

 three articles. The frontal lamina is narrow and long, and has the 

 anterior extremity rounded. 



The first segment of the thorax is nearW twice as long as any of 

 those following. The sevi^ntli is a little shorter than the sixth. The 

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

 An arched carina crosses all the epimera obliquely. The outer post- 

 lateral angle of the first two epimera is I'ounded; that of the last two 

 acutely produced beyond the posterior margin of the segments. 



The first segment of the abdomen is partly concealed by the seventh 

 thoracic segment. The posterioi- margin of the second, third, fourth, 

 and fifth segments is tuberculate. On all of these segiueuts there is a 



Fio. 132.— ExocoRALLAXA ANTiLLENsis. <), Maxilliped. X 27J. b. Mandible, x 27^ r. Second 

 MAXiij.A. X 27}. ri, First MAXILLA (outer and INNER LOBE). X 27j. e, Frontal lamina, x 27|. 



median depression, in the center of which is a small tubercle, one for 

 each segment, with the exception of the fifth, which has two tubercles 

 in longitudinal series. The sixth or terminal segment is triangular 

 with apex acute and furnished with a few short spines. There is a 

 median longitudinal depression extending the length of the segment, 

 on either side of which the dor.sal surface is hirsute. At the base of the 

 segment are two tubercles, one on either side of the median depression. 

 On either side of these, near the lateral margin and at the base of the 

 segment, are two other tu})ercles, the one nearest the lateral margin 

 being a little anterior to the other. Halfwa}' between the base and 

 the apex of the segment the lateral margin is cleft on either side. 

 The inner branch of the uropoda is wide and has the outer post-lateral 

 angle produced in an acute tooth; the inner posterior margin is crenu- 

 late and armed with spines. The outer branch is as long as the inner 

 branch, is half as wide, and is produced in an extremity teriuinating 

 in two subequal teeth. The inner angle of- the peduncle extends a 



