Pacific Coast of North America. '2,11 



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 terminal segment has the upper surface 

 smooth. This segment terminates in two long divergent 

 spines. There is a single spine on the lateral margin on 

 either side halfway down 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 Harbour, Aleutian Islands, 

 10 fathoms, co lected by Mr. W. H. Dall. 



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



Our species differs from A. Murdochi in the absence of 

 spines on the third joint of the second pair of antennas; 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 tlie anterior part of the head, 

 while in A. Murdochi there are three, and of two spines on 

 the posterior part, while in A. 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 the basal joint of the 

 legs, while in A. Murdochi there is but one spine on the basal 

 joint. 



This species is also distinguished from A. hystrix in the 

 presence of a single median spine on the anterior part of the 

 head, while in A. hystrix there are two, one on either side of 

 the median line and widely separated ; in the presence of two 

 spines on the posterior part of the head, while in A. hystrix 

 there are four ; in the absence of the double row of spines on 

 the terminal segment of the body ; and in the absence of the 

 spine at the articulation of the third joint of the second pair 

 of antennas. 



64. Arcturus Murdochi, Benedict. 



Arcturus Murdochi, Benedict, Proc. Biol. Soc. Washington, xii. 1898, 



pp. 49, 50. 

 Bab. Point Franklin, Alaska. 



65. Arcturus glaber *, Benedict. 

 Arcturus glahrus, Benedict, Proc. Biol. Soc. Washington, xii. 1898, 



p. 46. 

 Hah. Bering Sea. 



* glabrus bj error. 



[To be continued.] 



