258 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.10 



Orbinia johnsoni (Moore) 



Aricia johnsoni Moore, 1909, pp. 260-262, pi. 8, figs. 30-33. 



This occurs in clean sandy beaches at Dillon Beach ; in life it is green- 

 ish with a red cast. Length is 60 to 90 mm. 



Family Spionidac 

 Key to Species 



1. With a modified fifth setigerous segment, provided with heavy 

 hooks 2 



1. Without such a modified segment 5 



2. Branchiae already present in front of modified segment . . . 

 Boccardia 3 



2. Branchiae not present in front of modified segment .... 

 Polydora 4 



3. Posterior segments with strong, recurved hooks; branchiae pres- 

 ent on anterior segments 2 and 3 B. uncata 



3. Posterior segments without strong, recui"ved hooks; branchiae 

 present on anterior segments 2, 3, and 4 . . . B. proboscidea 



4. Branchiae few, first present from segment 10 or 11 ; tiny; boring 

 in encrusting corallines P. giardi 



4. Branchiae numerous, first present from segment 7; larger; inhab- 

 iting mud flats P. brachycephala 



5. With a single pair of branchiae, these broad, foliose, inserted 

 immediately behind paired palpi ; second setiger with a dorsal 



membrane; inhabits soft tubes on mud flats; tiny 



Streblospio benedicti 



5. Without such branchiae or dorsal membrane 6 



6. Branchiae present from first setiger, continued throughout 

 Spio 



6. Branchiae first present from second setiger 



Nerine cirratidus 



6. Branchiae first present much farther back 



Pygosp'io californica 



Polydora brachycephala Hartman 



Hartman, 1936, pp. 48-49, figs. 3-5. 



In Tomales Bay and Bodega Lagoon this is common among and 

 below beds of Cirriformia spirabrancha (see below). Length is 30 to 50 

 mm. 



