282 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.10 



dorsal side, have heavy, black eyespots, often 5 or 6 on a radiole. The 

 collar consists of a pair of smaller dorsal lobes, separated from each other 

 by a deep median cleft, and from the lateral lobes by a wide dorsolateral 

 notch ; it extends laterally and ventrally in a gradually rising membrane 

 and terminates in oblique ventral lobes separated by a deep midventral 

 incision. Length is 45 mm or over. 



Pseudopotamilla socialis, new species 

 Plate24, Figs. 53-58 



Many collections come from sponge masses at Tomales Point, ocean 

 side, and fewer in ascidian clusters. Tubes radiate out from the sponge 

 mass so that the distal ends project slightly from the surface of the sponge; 

 when extended, individuals lie with the tentacular crown covering much 

 of the surface of the sponge mass. Color in life and presei-ved is pale, or 

 tinged with dusky pigment and there are dark eyespots on the radioles. 

 Total length is only 20 to 25 mm, width about 1 mm in the thoracic 

 region. Number of segments includes 6 to 8 thoracic and 50 or more 

 abdominal segments. 



The tentacular crown consists of about 8 pairs of radioles; they are 

 entire, those on the ventral side are shortest, increasing gradually in 

 length dorsally. Radioles are provided with a double row of pinnae, have 

 only a short free end distally, as typical of the genus. Eyespots are vari- 

 able, sometimes are totally lacking, or occur singly, or may number 4 or 

 5 on a radiole. They are usually limited to the lateral radioles, near their 

 midlength. Eyes are large, dark brown, circular. The number and distri- 

 bution of eyespots are highly variable in this species, as in some other 

 sabellids {Eudistylia, below). The dorsal edge of the tentacular base is a 

 short, thin, straight membrane. 



The collar is 4 lobed; its dorsal portion consists of a pair of low, 

 oblique flaps, widely separated from the lateral ones by a deep dorsolateral 

 cleft; except at its medial portions it leaves much of the peristomium 

 exposed. Lateral lobes rise abruptly above the dorsolateral clefts and con- 

 tinue ventrally to form high, oblique ventral flaps, their tips more or less 

 prolonged, attenuate. 



Ventral scutes are rectangular, broader than long, without markings 

 or indications of transverse bisections at the sides. Abdominal segments 

 are clearly marked, as long as broad, or shorter. The first thoracic setiger 

 is provided, on each side, with a notopodial fascicle of 6 longer (pi. 24, 

 fig. 54) and 7 shorter (pi. 24, fig. 55) bilimbate setae, disposed in 2 

 transverse rows. From the second, notopodia are provided with slender 



