734 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



Flustrellidae, but the morphological differences in the aperture, the 

 presence of the prominent communication pores, and the lack of keno- 

 zooecial spines warrant the separation of this genus into a distinct family. 



Genus PHERUSELLA Soule, 1951 



Zoaria coriaceous, incrusting, or arising from incrustations in branch- 

 ing flabellate, flattened projections. The distal ends of the zooecia rise 

 into prominent tubular processes, which bear the aperture. When the 

 polypide is retracted, the apertures appear square to transversely quad- 

 rangular in shape. The lateral walls and the distal walls are pierced by 

 prominent multiporous septulae provided with heavily chitinized rims, 

 apparently a unique character in the Ctenostomata. Genotype: Flustra 

 tubulosa (Solander), 1786. The genus Pherusa Lamouroux, 1816, is 

 preoccupied by Pherusa Oken, 1807. The name Pherusa had also been 

 proposed by Leach, 1814, and Rafinesque, 1815. 



Pherusella brevituba Soule, 1951 

 Plate 78, fig. 2 



Pherusella brevituba Soule, 1951:368. 



The chitinous zoaria are a light brown in color, leathery in appear- 

 ance, and form prominent incrustations upon the holdfasts and blades 

 of algae. When the zoaria are strictly incrusting, they are unilaminar, 

 or they may form erect fan-like "fronds" that are bilaminar, back to 

 back, where the zoarial growth exceeds the limits of the algae thalli. 



The zooecia are elongate with considerable variation in shape, from 

 imperfectly rectangular to hexagonal, averaging about 0.80 mm in length 

 and 0.40 mm in width. Normally the individual zooecia are distinct, 

 clearly defined by the lateral walls. The zooecial walls are perforated 

 by well marked compound interzooecial communication pores having an 

 average diameter of 0.02 mm. The rims of the communication pores 

 are strengthened by heavy chitinous rings. Within this ring are four 

 minute perforations piercing a thin chitinous diaphragm. 



The distal portion of each zooecium is raised to form a short but 

 prominent tubular process bearing the aperture. The upper extremity 

 of this tubular process is square to transversely quadrangular in shape. 

 The tentacles number 23. 



This species has been taken off Portuguese Bend, California ; collected 

 in the intertidal zone at Punta Baja, Rosario, Lower California, by 

 E. Y. Dawson ; and found on the holdfast of algae washed ashore near 

 the Santa Barbara-San Luis Obispo county line, southern California. 

 The range in depth is from intertidal to 8 fathoms. 



