NO. 1175. ISOPODS OF THE PACIFIC COAST— RICHARDSON. 819 



ANALYTICAL KEY TO TRIBKS.OIJ StII'KHKAMII.IKS OK I'ACIKK; COAST ISOPODA. ' 



a. L<^fj;8 of first pair clicliform. llropocla tcruiiual. I'lcopoda, wlicii distinctly 



<loveloi)cd, oxcliisivcly natatory I. Ciielikeka (p. 811)). 



a' . Le^s of (irst i)air not chclilbrm. 

 h. lJro]>o(la l;i(eral. 



c. llropoda lonniiifj; i (({bother witli the terminal sojjnientof tlio niotasonieacandal 



fan. I'leopoda for tiie most part natatory II. Fi.ahkllikkua (p.820). 



c' . llropoda valvolik(», indexed, archinj^ over the plcopoda, which to a great 



extent are branchial , III. Val\ii'Bka (p. 842). 



6'. llropoda terminal, 

 c. Free forms. 

 d. rieopoda exclusively branchial, gcuer.illy covered by a thin opercular plate 



(the niodilied first pair) IV. Asellota (p. SHG), 



d' . Plcopoda litted'for air-brciathing V. Omscoidka (p. 8f)0). 



o'. Parasitic forms VI. Ei-icakidea (p. 8G7). 



I. CHELIFERA. 

 Family 1. TANAID^E. 



Body scarcely attenuated behind. Mandibles without palp. Coxal 

 plates incous[)icuous. Superior aiiteniiii' with one multiarticulate 

 rtagellum. Anterior niaxilhe with only a single masticatory lobe; j^os- 

 terior ones quite rudimentary. Second ])air of legs ambulatory in 

 character. Epignath of nuixillipeds narrow, falciform. 



1. TANAIS Audouin and Mihie-Edwards. 



AnteuDic short, subecjual. Pleon five-Jointed; fourth joint short; 

 fifth joint terminated byapairof single brani-Iied (ihimentary iiropoda. 

 Only three pairs of pleopoda. Palp of anterior ma.\ill;e biarticulate. 

 Eyes well developed. Superior antennie three-articulate, with small 

 terminal Hagellum. 



analytical key to TIIK Sl'KCIES OK TANAIH. 



a. Inferior antennse scarcely half the length of superior antenna;. Peroiopoda hav- 

 ing the first three Joints short and broad, affixed to sides of pereion like plates 

 of mail 1. Tanain loricatus Spence IJate. 



a'. Inferior and sMi)crior aQtenuu) of nerrly equal length. Pereiopoda with joints 

 not dilated, slender 2. Taiiais alascensls, new species. 



I. TANAIS LORICATUS Spence Bate. 



Tanain I or icatiin SvKNCii Hate, Lord's Naturalist in liritish C(ilmn)>i;i,, II (18GG), 

 p. 282. 



Habitat — Esquiraault Harbor, British Columbia. 



2. TANAIS ALASCENSIS, new species. 



Body three and a half times longer than broad. 



Head large, narrowed anteriorly. Frontal margin almost straight. 



' Sars's analytic key has been used with slight modifications. Sars's "An Account 

 of the Crustacea of Norway," II, Isopoda (1896), Pts. I, II, p. 3. 



