ISOPODS OF NORTH AMERICA. 



329 



from the segments, are eoiispicuous from a dorsal view, and are pro- 

 duced at the sides in processes which are rather bknit at their 

 extremities. 



The first two seo-nieiits of the abdomen are short. The t(M-niinal 

 segment is long and pi'oduced to an extremit}'^ which has a V-shaped 

 excavation. The length of the terminal segment is a little less than one- 

 fourth that of the entire bod}', being 8 mm. long. Near the bas(^ is a 

 transverse depression marked on either side by a blunt expansion of 

 the lateral margin, probably indicative of a coalesced segment. The 

 first four pairs of legs are slender, directed forward, and densely 

 covered with long, slender hairs on the inferior margins of all the 

 articles. The first pair of legs is shorter than the three following pairs. 

 The last three pairs of legs are ambulatory. 



ARCTURUS LONGISPINUS Benedict. 



Arcturus longispinus Benedict, Proc. Biol. Soc. Washington, XII, 1898, pp. 44- 

 45.— Richardson, Proc. U. S. Nat. Mus., XXI, 1899, ]>. 854; Ann. Mag. 

 Nat. Hist. (7), IV, 1899, p. 275; American 

 Naturalist, XXXIV, 1900, p. 229. 



Locality. — Aleutian Islands. 



Dej>th. — 55 fathoms. 



Body narrow, elongate, nearly five times 

 longer than wide, 7 mm. : 85 nun. 



Head wider than long, 7 mm. : 4 mm., with 

 the anterior margin deepl}' excavate l)etween 

 the produced antero-lateral angles. The eyes 

 are small, round, composite, and situated at 

 the sides of the head halfway between the 

 antero-lateral angles and the posterior margin. 

 There are two extremely long spines, 7 mm. 

 in length, situated about the middle of the 

 head between the eyes, one on either side of 

 the median line. The first pair of antenna 

 have the basal article long and somewhat 

 dilated, about twice as long as wide; the sec- 

 ond and third articles are subequal in length, 

 each being half as wide as the basal article and 

 much shorter; the fourth article is about one 

 and a half times longer than tlie third. The 

 first antenna^ extend to the end of the second 

 article of the peduncle of the second antenna}. 

 The basal article of the second antennae is 

 short; the second article is 3 mm. long; the third is four times as 

 long as the second, or 12 nun. long; the fourth is 17 mm. in length; 

 the fifth is 15 mm. The flagellum is composed of eight articles, the 



Fig. 360.— Arcturus longi- 

 spinus (Ap-TER Benedict). 

 X IJ. 



