of the Pacific Shores of North America, 505 



thoracic segment. Abdomen subrectangular, broadest ante- 

 riorly, nearly twice as long as broad, and equalling in length 

 the four preceding thoracic segments taken together; its 

 sides slightly concave ; posterior extremity with a deep con- 

 cavity, terminating on either side in a sharp angular pro- 

 jection or tooth. First and second segments of the abdo- 

 men sufficiently well marked, the third also distinct on the 

 sides : — the three occupying the anterior third of the length 

 of the abdomen. Outer antennae reaching the fourth tho- 

 racic segment; peduncle rather stout ; flagellum 17-articu- 

 late. Basal article of inner antennae greatly expanded, 

 suborbicular. The opercular (first) pair of abdominal feet 

 are broad, with the terminal joint square. Inner sides of 

 ambulatory feet with short setae. Color greenish yellow, 

 with a median line of dark-red. Length, 1.7 ; breadth, 0.33 

 inch. Proportion of breadth to length, 1 : 5.15. 



This species resembles the Mediterranean I. hectica in 

 general appearance, and is not liable to be confounded with 

 any other species found on our western coast. 



The only specimen known was dredged in the Straits of 

 DeFuca, opposite Fort Townsend, by Capt. Murden. 



Mus. Smithsonian. 



STENOSOMA GRACILLIMUM. Dana. 

 Stenosoma gracillimum, Dana ; Proc. Acad. Nat. Sci. Philad. 1854, vii. 175. 



Hab. California, (Le Conte.) 

 Mus. of Prof. Dana. 



SPHEEILLO AFFINIS, Dana. 

 Sphevillo affinis, Dana. Proc. Acad. Nat. Sci. Philad. 1854, vii. 176. 



A terrestrial species found in California by Dr. Le Conte. 

 Mus. of Prof. Dana. 



JOURNAL B. S. N. H. 65 



