158 Miss H. Richardson on the Isopods of the 



many suggestions obtained from his excellent work on the 

 Crustacea of Norway. In many places his synopses of the 

 families and genera have been used in entirety. Other 

 authors have been most helpful : Hansen on the Cirolanidajj 

 Schiodte and Meinert on the Cymothoidge ; Budde-Lund on 

 the Oniscida3 ; and others, to whose works specific references 

 are made. 



The present paper is based on material contained in the 

 U.S. National Museum. 



Analytical Key to Tribes or Superfamiltes of Pacific Coast 

 Isopoda *. 



a. Le?s of first pair clieliform. Uropoda terminal. 

 Pleopoda, wheu distinctly developed, exclu- 

 sively natatory ' I. Chelifera. 



a', Le{?s of first pair not clieliform. 

 h. Uropoda lateral. 



c. Uropoda forming together with the terminal 

 segment of the metasome a caudal fan. 



Pleopoda for the most part natatory II. Flabellifera. 



c'. Uropoda vah'e-like, inilexed, arching over 

 the pleopoda, which to a great extent are 



branchial III. Valvifera. 



6'. Uropoda terminal. 

 c. Free forms. 



d. Pleopoda exclusively branchial, generally 

 covered by a thin opercular plate (the 



modified first pair) IV. Asellota. 



d'. Pleopoda fitted for air-breathing V. Onisooidea. 



c'. Parasitic form? VI. Epicaridea. 



I. CHELIFERA. 



Family I. Tanaidae. 



Body scarcely attenuated behind. Mandibles without palp. 

 Coxal plates inconspicuous. Superior antenna3 with one 

 multiarticulate flagellum. Anterior maxillaj with only a 

 single masticatory lobe ; posterior ones quite rudimentary. 

 Second pair of legs ambulatory in character. Epignath of 

 maxillipeds narrow, falciform. 



1. Tanais, Audouin & .Milne- Edwards. 



Antennfe short, subequal. Pleon five-jointed ; fourth 

 joint short ; fifth joint terminated by a pair of single branched 

 filamentary uropoda. Only three pairs of pleopoda. Palp of 

 anterior maxillai biarticulate. Eyes well developed. Supe- 

 rior antennae three-articulate, with small terminal fiagellum. 



* Sara's analytic key has been used with slight modifications, Sara's 

 ' An Account of the Crustacea of Norway,' 11., Isopoda (1896), pta. i., ii. 

 p. 3. 



