448 U.S. NATIONAL MUSEUM BULLETIN 2 71 



KEY B 



1. Palp of maxilla 1 uniarticulate 2 



Palp of maxilla 1 biarticulate Mesoproboloides 



2. Mandibular palp 1-articulate or absent Stenothoides 



Mandibular palp 2- or 3-articulate Mesometopa 



KEY C 



1. Palp of maxilla 1 uniarticulate 2 



Palp of maxilla 1 biarticulate 4 



2. Mandibular palp absent Parametopa 



Mandibular palp 1-articulate Stenula 



Mandibular palp 2- or 3-articulate 3 



3. Accessory flagellum absent Metopa 



Accessory flagellum 1-articulate Prometopa 



4. Mandibular palp absent 5 



Mandibular palp present 6 



5. Accessory flagellum 1-articulate Microstenothoe 



Accessory flagellum absent Stenothoe 



6. Mandibular palp 1-articulate Prostenothoe 



Mandibular palp 2- or 3-articulate 7 



7. Accessory flagellum absent Proboloides 



Accessory flagellum 1- or 2-articulate Metopoides 



Genera of Stenothoidae 



Mesometopa Gurjanova 



Mesometopa Gurjanova, 1938. 



Type-species: Metopa esmarki Boeck, 1872 (original designation). 



Mandibular palp 2- or 3-articulate; palp of maxilla 1 uniarticulate; 

 article 2 of pereopod 4 linear, of article 5 expanded. Species: 4, 

 arctic-boreal, littoral. 



Mesoproboloides Gurjanova 



Mesproboloides Gurjanova, 1938. 



Type-species: Metopella cornuta ScheUenberg, 1926a (original 

 designation). 



Mandibular palp 3-articulate; palp of maxilla 1 biarticulate; arti- 

 cle 2 of pereopod 4 linear, of pereopod 5 expanded. Species: 2, 

 subantarctic, littoral. 



Metopa Boeck 



Metopa Boeck, 1871.— Stebbing, 1906. 

 Metopina Norman, 1900b (homonym, Diptera). 

 Sthenometopa Norman, 1902. 



Type-species: Leucothoe clypeata Kr0yer, 1842 (selected by Boeck, 

 1876). See Gurjanova, 1948, 1951; Shoemaker, 1955. 



