300 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 7 



This is the commonest intertidal spionid in California, inhabiting par- 

 ticularly soft, reef-buikling shales, narrow interstices in harder rocks, and 

 fine crevices among other suitable hard objects. If in shales, it occurs 

 usually in vertical or oblique burrows made by the inhabitant; if in 

 crevices, these are usually in oblique positions, the adjacent hard surface 

 slightly grooved by the back-and-forth movement of the worm. A thin, 

 mucoid, dcbiis-covercd tube covers it. The abundance of this species is 

 often so great as to form a conspicuous part of the intertidal fauna. It may 

 be found in low-lying, flat reefs, especially if these be of soft limestone or 

 shale. AVhen conditions are favorable, as they are in the vicinity of reefs 

 at Moss Beach, San Mateo County, at Point Fermin, at Point Conception 

 and other places, the burrows may be numerous, closely spaced, only a few 

 millimeters from one another. Also, in high tidal pools, where tempera- 

 ture/salinity ratios may fluctuate greatly, this species successfully main- 

 tains itself. 



B. proboscidca is not known to occur outside California. Its bathy- 

 metric range extends from the high intertidal pools to moderately low- 

 water line; it has never been recovered from dredged collections. It is 

 tolerant to salinities ranging from strictly marine to brackish, such as are 

 found in the eastern end of San Francisco Bay, in the vicinity of Berkeley; 

 its presence in high tidal pools indicates that it tolerates high salt content. 

 Its ccologic niche is soft stones or narrow rocky crevices; it has never 

 been found associated with sandy beaches or a strictly soft substratum. 



B. prohoscidea belongs to a small group in which the heavy spines of 

 the modified fifth segment are of 2 kinds — ( 1 ) stout, smooth, falcate, and 

 (2) bristle topped, in which the bristled area is limited to a region beyond 

 the thickest part (pi. 46, fig. 24). The prostomium is prolonged anteriorly 

 so as to extend beyond the peristomium; it is smooth, entire at its frontal 

 margin (pi. 46, fig. 22). A caruncle extends posteriorly between the 

 palpal bases to the posterior margin of the third setiger. A considerable 

 sooty pigmentation is usually to be seen in the grooves between pro- 

 stomium and peristomium. On the ventral side, the anterior portion of 

 the prostomium has a median groove (pi. 46, fig. 23). In adult males, 

 parapodial glands are present from the seventh to ninth segment; sper- 

 matozoa from the fourteenth; nephridia are greatly enlarged in this 

 region. Hooded hooks are first present from the seventh setiger. 



The interesting development of this species was first called to the 

 author's attention several years ago by Professor S. F. Light, while at 

 IVIoss Beach, near San Francisco. During the spring and summer months, 



