356 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



59. Genus IDOTHEA Fabricius 1799. 



Flagellum of second antennse multi-articulate. Maxillipeds with a 

 palp composed of four articles. Epimera of all the segments of the 

 thorax, with the exception of the first, distinctly separated from the 

 segments. Abdomen composed of three segments, with a suture line 

 on either side at the base of the terminal segment, indicating another 

 partly coalesced segment. 



ANALYTICAL KEY TO THE SPECIES OF THE GENUS IDOTHEA. 



o. Body slender, linear, filiform. 



b. Terminal segment of body truncate at its posterior extremity; post-lateral an- 

 gles not prominent Idothea gracillima (Dana) 



b' '. Terminal segment of body not truncate at its extremity; post-lateral angles 



prominent, 

 c. Post-lateral angles of terminal segment prominent and separated by a notch 



from the triangular middle portion. 

 d. Terminal segment with middle portion obtuse and produced at the apex in 



a small point. Lateral angles obtuse Idothea urotoma Stimpson 



d' . Terminal segment with middle portion of posterior extremity very acutely 



produced. Lateral angles acute Idothea fewkesi, new species 



</. Post-lateral angles not separated by a notch from the subtriangular middle 

 portion, which does not bear a tooth at the middle; the line from the apex 



to the lateral angle is straight Idothea rectilinea Lockington 



a'. Body oblong-ovate. 



b. Terminal segment of body truncate at its extremity Idothea metallica Bosc 



V . Terminal segment of body not truncate at its extremity. 

 c. The epimera of all the segments, from the second to the seventh inclusive, 



occupy the entire lateral margins of the segments Idothea battica (Pallas) 



</. The epimera of all the segments of the thorax, from the second to the 

 seventh inclusive, do not occupy the entire lateral margins of the segments. 

 d. Terminal segment of body with distinct and prominent post-lateral angles. 

 Basal article of the first pair of antennae very much dilated. 



Idothea ochotensis Brandt 



d'. Terminal segment of body without distinct post-lateral angles, the sides 

 of the abdomen tapering to a pointed extremity. Basal article of first 

 pair of antennae not dilated Idothea phosphorea Harger 



IDOTHEA GRACILLIMA (Dana). 



Stenosoma gracillimum DANA, Proc. Acad. Nat. Sci. Phila., VII, 1854, p. 175. 

 STIMPSON, Bost. Jour. Nat. Hist., VI, 1857, p. 505. 



Ido'hea gracillima MIERS, Jour. Linn. Soc. London, XVI, 1883, p. 35. RICHARD- 

 SON, Proc. U. S. Nat. Mus., XXI, 1899, p. 844; Ann. Mag. Nat. Hist, (7), 

 IV, 1899, p. 264; American Naturalist, XXXIV, 1900, p. 226; Harriman 

 Alaska Expedition, Crust., X, 1904, pp. 216-218; Proc. U. S. Nat. Mus., 

 XXVII, 1904, pp. 661-663. 



Localities. California; Bolinas, California. 



The description of this species given by Professor Dana is very short 

 and rather vague. He describes the body as extremely slender and 



