1SOPODS OF NORTH AMERICA. 



345 



dinal line, the two center ones being the longest, although all are .very 

 long. The fourth segment is twice as long as any of the other seg- 

 ments, and has a transverse constriction on the posterior half of the 

 segment. On the anterior portion are six spines, three on either side 

 of the median line, the four outer ones being in a straight line, the 

 inner two below this line. On the posterior portion are six spines 

 also, three on either side of the median line. The fifth thoracic seg- 

 ment has twelve spines, six on either side of the median line. The 

 sixth segment has ten spines, 

 five on either side. The sev- 

 enth and last segment has 

 eight spines, four on either 

 side. 



The abdomen is composed 

 of two segments. The first is 

 short, with twelve spines, six 

 on either side of the median 

 line, the four inner ones being 

 arranged in two longitudinal 

 series, the two upper ones 

 being small, the two lower 

 ones very long. The termi- 

 nal segment has the upper 

 surface smooth. This seg- 

 ment terminates in two long 

 divergent spines. There is a 

 single spine on the lateral 

 margin on either side about 

 the middle of the segment, 

 and another near the base of 

 the segment. The three anterior pairs of legs have each two spines 

 on the coxal joint and one spine on the basis. The body increases in 

 width from the first to the fourth segment, and then decreases in width 

 from the fourth to the terminal segment. 



One specimen from Kyska Harbor, Aleutian Islands, 10 fathoms, 

 collected by Dr. W. H. Dall. 



Type. Cat. No. 22581, U.S.N.M. 



This species differs from P. murdochi in the absence of spines on the 

 third joint of the second pair of antennae; in the greater length of this 

 joint in relation to the preceding joint; in the greater length of the two 

 following joints; in the presence of a single spine on the anterior part 

 of the head, while in P. murdochi there are three, and of two spines on 

 the posterior part, while in P. murdochi there are four; in the absence 

 of two small spines just below the constriction in^the fourth segment; 

 in the absence of the row of spines on the terminal segment of the 

 body; and in the presence of two spines on the coxal joint and one on 



FIG. 373. PLEUROPRION INTERMEDIUM, x 10. 



