292 allan hancock pacific expeditions vol. 7 



Key to the 1 1 Genera of SPIONIDAE from California 



1. With a modified segment 2 



1. Without a modified segment 5 



2. Sixteenth segment modified ; branchiae present from the first 



setiger; pygidium with 2 cirri 



Movants (M. duplex Chamberh'n) 



2. Fifth segment modified; branchiae present after the first setiger; 

 pygidium usually disklike (rarely with cirri) 3 



3. Branchiae present anterior and posterior to the modified segment 

 Boccardia, p. 299 



3. Branchiae present only posterior to the modified segment 

 Polydora, p. 305 



4. Without branchiae; prostomium with laterally directed processes 

 at its anterior margin; anus with cirri . . Spiophanes, p. 296 



4. With branchiae; prostomium with or without such processes; 

 anus with or without cirri 5 



5. With only one pair of branchiae, these simple, inserted just poste- 

 rior to the paired palpi ; second segment with a raised dorsal 

 membrane ; pygidium simple, without disk or cirri .... 

 Streblospio {S. lutincola Hartman) 



5. With more than one pair of branchiae; without such raised dor- 

 sal membrane on second segment; pygidium disklike or sur- 

 rounded by cirri 6 



6. Prostomium with articulating lateral horns at its frontal margin ; 

 branchiae present from second setiger and on most segments 



thereafter; uncini distally tridentate 



Rhynchospio (R. arenincola Hartman) 



6. Prostomium without articulating horns; branchiae present from 

 second setiger or later; uncini bidentate to multidentate . . 7 



7. Branchiae pennate, limited to a few anterior segments; uncini 

 distally multidentate .... Prionospio (P. alata), p. 298 



7. Branchiae simple, cirriform or straplike, present on several to 

 many segments; uncini usually bidentate (sometimes tridentate) 8 



8. Successive neuropodia in a long posterior region connected by in- 

 terramal pouches Laonice, p. 293 



8. Without such neuropodial pouches 9 



