2 ( .H> BULLETIN f>4, UNITED STATES NATIONAL MUSEUM. 



The basal article of the .second antenna 1 is very short; the second and 

 third are longer than the first and subequal; the fourth and fifth are 

 about equal and each is one and a half times longer than the third. The 

 flagellum is composed- of twelve articles. The second antennae extend 

 a little beyond the posterior margin of the first thoracic segment. The 

 maxilliped has a palp of five articles. The palp of the mandibles is 

 composed of three articles. The frontal lamina is large and conspicu- 

 ous, and has the anterior division wide and long, with the post-lateral 

 or ventral angles drawn out, giving it somewhat of a horse-shoe shape. 

 The clypeus is transversely oblong, and fits into the concavity of the 

 posterior part of the frontal lamina; its posterior margin is fringed 

 with cilia. 



The segments of the thorax are equal in length. The epimera are 

 not distinct from the segments. The lateral margins are nearly 

 straight. 



The abdomen is composed of two segments. The first segment is 

 about as long as the last thoracic segment and has one suture line on 

 either side. The terminal segment is triangular, with the apex bluntly 

 rounded. The inner fixed branch of the uropoda is as long as the ter- 

 minal segment. The outer moveable branch is about half as wide as 

 the inner branch, is very pointed at its extremity, and when folded is 

 not quite as long as the inner branch, being 1 mm. shorter. The 

 length of the inner branch is 5 mm. ; that of the outer branch is 4 mm. 



The legs are all ambulatory. 



EXOSPH^ROMA OREGONENSIS (Dana). 



Sphseroma oregonensis DANA, Proc. A cad. Nat. Sci. Phila., VII, 1854-55, p. 177; 



U. S. Expl. Exp. Crust., XIV, 1853, p. 778, pi. LII, fig. 4. STIMPSON, Boat. 



Jour. Nat. Hist., VI, 1857, p. 509. 



Spltseroma olivacea LOCKINGTON, Proc. Cal. Acad. Sci., VII, 1877, Pt. 1, p. 45. 

 Sphseroma oregtmenxis RICHARDSON, Proc. U. S. Nat. Mus., XXI, 1899, p. 836; 



Ann. Mag. Nat. Hist., (7), IV, 1899, p. 180; American Naturalist, XXXIV, 



1900, p. 223; Harriman Alaska Exp. Crust., X, 1904, p. 214; Proc. U. S. Nat. 



Mus., XXVII, 1904, p. 659. 



Localities. Pacific Grove to Alaska; Popof Island (from fresh water), 

 Yakutat, and Glacier Bay, Alaska; Grenville Channel and Lowe Inlet, 

 British Columbia; Angel Island, San Francisco Bay, California 

 (Lockington Coll.); Gulf of Georgia; Alert Bay and Kadiak, Alaska; 



ft The following description of Dana's, although concise, gives most of the essen- 

 tial characters of the species: Corpus Iseve. Segmentum caudale breve, postice latis- 

 sime rotunatum, supra Iseve. Styli caudales abdomen non superantes, lamella internd 

 multo longiore quam externa, fere obtusd, externa obtusd. Flagella antennarum 1 

 marum 2 darurnque 12-14 articulata. 



Body smooth. Caudal segment short, very broadly rounded behind, smooth 

 above. Caudal stylets not reaching beyond line of extremity of abdomen; inner 

 lamella much the longer, nearly obtuse; outer obtuse. Flagella of antenna of both 

 pairs twelve to fourteen jointed. Length of body four and a half lines. 



