308 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 7 



last 6 segments; those in the fifth and sixth last segments are unusually 

 conspicuous bundles; those in the last 4 segments are much smaller; the 

 neuropodia of these segments are provided with a series of about 4 hooded 

 hooks and a lanceolate seta. 



The pygidium is a narrow collar, not much wider than the posterior 

 end of the body. A simple gregarine has been found in the alimentary 

 tract. 



This is the first record of P. armata from the eastern Pacific. Okuda 

 (1937, pp. 230-231) has recorded it from Japan, associated with coral, 

 algae, sponge, and a mollusk. 



Polydora ciliata (Johnston) 

 Plate 48, Fig. 40 



Fauvel, 1927, pp. 49-50, fig. 16; Berkeley, 1936, p. 472; Okuda, 1937, 

 p. 230, fig. 9. 



Numerous collections from Point Richmond, San Francisco Bay, 

 Muir Beach, San Mateo County, and others from Mission Bay near San 

 Diego, all from the intertidal zones, are attributed to this species. They 

 agree with descriptions indicated in the synonymy above. The heavy modi- 

 fied spines of the fifth setiger are falcate, with a lateral sheath ; their com- 

 panion pennoned setae are proportionately large (pi. 48, fig. 40). 



P. ciliata has been widely reported from many seas ; it is known espe- 

 cially for perforating calcareous shells and has been shown to be injurious 

 to shell-fish industries (Lunz, 1940, p. 310). 



Polydora commensalis Andrews 



Andrews, 1891, pp. 25-35, 2 pis.; Berkeley, 1936, pp. 469-471 ; Annen- 

 kova, 1938, p. 178, fig. 14. 

 This has been recovered from shells of Ilyanassa occupied by hermit 

 crabs, from beaches in southern California. Unique features of this species 

 include : ( 1 ) the large robust body with short, thick palpi and short pro- 

 stomium; (2) broad, straplike branchiae; (3) modified falcate spines in 

 the fifth segment, with a long, narrow sheath. First described from Beau- 

 fort, North Carolina, it has since been reported from British Columbia 

 (Berkeley) and the North Japan Sea (Annenkova). Another specimen 

 in our collections comes from Mazatlan, Mexico (collected by Dr. Mar- 

 tin W. Johnson), also found with a hermit crab. 



