1923] NATUK\L SCIENCES OF PHILADELPHIA 253 



eight opercular annulations is thick and stony, very rough with 

 overlapping plates that rise to a median ridge. 



Stations 4550, off Point Pinos Lighthouse, 50-57 fathoms, green 

 mud and rocks (type) ; 4420, off San Nicolas Island, 32-33 fathoms, 

 fine gray sand. 

 Protis pacifica sp. nov. 



Branchiae as packed closely in tube form a terete mass in which 

 the individual gills are straight except for a slight spiral twist and 

 distal inflection. Branchiophores small, low and of nearly even 

 height, not prolonged ventrally or spirally coiled as in Protula. 

 Radioles 18 pairs, their outer faces swollen and turgid but neither 

 angulated nor margined, coherent l)ut not united by an inter- 

 branchial membrane. Barbs numerous, very small, strongly 

 ciliated and continued practically to the extreme end of the radioles. 



Oral membranes not discernible. Collar and mantle wide and 

 prominent but much broken so that specific characters cannot be 

 determined. Thorax and abdomen terete, the latter becoming 

 somewhat depressed at the caudal end. Thoracic somites 8 (7 

 setigerous), abdominal 64, or possibly more, as several may have 

 been missed in the mutilated middle region. First three or four 

 abdominal segments elongated, the remaining ones very short, 

 the last few abruptly tapered to a small simple pygidium. 



Thoracic setse all yellow, in i)rominent fascicles, the collar 

 fascicle at a higher level and directed considerably forward, the 

 other six erect and well separated. Abdominal fascicles very small, 

 erect, inconspicuous on anterior segments because of the shortness 

 of the setse but becoming elongated and much more conspicuous 

 at the caudal end. Six pairs of thoracic tori delicate, slightly 

 curved lines immediately behind and below the setae tufts which 

 they somewhat overlap. Abdominal tori shorter but more elevated 

 than the thoracic and glandularly thickened. 



Collar sette in two series of about twelve each, those of one 

 longer and stouter with a prominent basal fin bearing five or six 

 coarse teeth in a rounded crest, distad to which, following a broad 

 notch, is a narrow, finely denticulated blade, which gradually 

 tapers into a delicate, flexi])le, smooth capillary tip. The smaller 

 seta3 of the other series lack both basal fin and capillary tip 

 but are longer, with very narrow blade. Remaining thoracic 

 tufts are of three series of six or seven each all of the form of the 

 smaller collar seta? except that the tips are less prolonged. Thoracic 

 uncini very numerous and closely crowded in a series diminishing 

 in size ventrad and with the teeth directed cephalad. They have 

 the body restricted and a longer liorder bearing six or seven promi- 

 nent, acute curved teeth diminishing in size from below. Ab- 

 dominal setai usually but one, sometimes two, in a fascicle, similar 

 to the shorter thoracic setae, with a slight liml)us or fin and a slender 



