326 



ALLAN HANCOCK PACIFIC EXPEDITIONS 



VOL. 15 



Chart showing diagnostic characteristics of species of 



Aricidea (Aedicira) 



Aricidea (Aedicira) pacifica Hartman, 1944 



Aricidea pacifica Hartman, 1944d, pp. 316-317, pi. 27, figs. 8, 9. 



Collections.— 1450-42 (2) ; Newport Bay, December, 1941 (5) and 

 December, 1943 (2) all from low intertidal eel grass beds near the 

 mouth of Newport Bay, California, associated with rocks, mud, sand 

 and a richly diversified fauna. 



The prostomium is truncate, broader in front, and has a median 

 concavity; it narrows posteriorly. Branchiae are first present on the 

 fourth setigerous segment and number about 60 pairs. In the posterior 

 branchial region the branchiae are very long, attenuate and have slender 

 filamentous tips. 



In prebranchial segments all setae are slender and capillary. In 

 branchial segments the neuropodia have full fascicles of palisaded rows 

 of setae that emerge from neuropodia in stiff series and are directed 

 obliquely back. Each seta has a broad blade and terminates in an abrupt- 

 ly long, slender pointed tip, somewhat resembling a subuluncinus of the 

 Orbiniidae but without surface sculpturing. Abdominal segments have 

 setae of a single kind, all slender, capillary and in full, flowing fascicles, 

 those in a bundle appearing white in mass. Each is very slender and hair- 

 like. There are no modified hooks. 



A. (Aedicira) pacifica grossly resembles Aricidea fragilis (see above) 

 because of the large number of branchiae. In the first the prostomium is 

 truncate and excavate at its anterior margin ; in the second it is bluntly 

 conical or rounded in front. The first has only pointed setae in the ab- 

 domen, the second has modified bifid hooks in posterior neuropodia. 



Distribution. — Aricidea (Aedicira) pacifica is known only from 

 Newport Bay, California, in low intertidal zones, associated with a 

 mixed bottom covered with eel grasses. 



