ISOPODS OF NORTH AMERICA. 433 



The color of the species is a light brown, somewhat mottled. 



Prof. S. J. Holmes describes the type specimen" of this species, 

 which I have not been fortunate enough to obtain for examination. 

 The description given above is from specimens collected at Lake 

 Washington, Seattle, and which I still do not think differ from the 

 type as described by Professor Holmes in any essential characters. 

 The type specimen is imperfect, one uropod being gone and the other 

 with the inner branch partly regenerated. The specimens which 

 Professor Holmes collected at Point Arena have "caudal stylets 

 shorter than the abdomen," as is also true of my specimens, and 

 he considers the Point Arena specimens as young specimens of this 

 species. 



A slight difference in the length of the antennae often occurs among 

 the individuals of a species where the flagellum is multi-articulate. 

 It may be due to a difference in sex or a difference in age. 



The only important difference is in the fact that the three last seg- 

 ments of the thorax are entire in the type, as described by Professor 

 Holmes, whereas they are posteriorly notched in the specimens from 

 Lake Washington. The margins of the segments often appear entire 

 when the emargination is filled by the epimeron, so that without 

 having seen the type I would be unwilling to give a new name to the 

 specimens from Lake Washington, which are otherwise in so close 

 agreement with Professor Holmes's description. 



69. Genus C^ECIDOTEA Packard. 



Body narrow, elongate. Eyes wanting. Head large, not narrower 

 than the first thoracic segment and longer. Terminal segment of body 

 much longer than broad. 



ANALYTICAL KEY TO THE SPECIES OF THE GENUS C^CIDOTEA. 



a. Propodus of first pair of legs armed with one or more triangular processes. 



b. Propodus of first pair of legs armed with two long triangular processes and three 

 short ones. Uropoda about as long as the terminal segment of the body; the 

 inner branch of the uropoda is two-thirds as long as the peduncle; the outer 



branch is two-thirds as long as the inner branch dvcidotea stygia Packard 



//. Propodus of first pair of legs armed with a triangular process near the distal 

 end and with a long spine at the proximal extremity. Uropoda shorter than 

 terminal abdominal segment, about one-half its length; the peduncle is as 

 long as the inner branch; the outer branch is one- fourth shorter than the inner 



branch Cxcidotea nickajackeims Packard 



a'. Propodus of first pair of legs not armed with triangular processes, but edged 



inside with spines. 



'b. First pair of antennae, with flagellum composed of eleven articles, extend one- 

 third the length of the fifth article of the peduncle of the second antenna-. 



"Proc. Cal. Acad. Sci. (3), III, 1904, pp. 321-323. 



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