336 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 15 



Longosoma catalinensis Hartman, 1944 

 Plate 43, fig. 8 



Longosoma catalinensis Hartman, 1944d, p. 322, pi. 27, figs. 1-3. 



Collection.— 2153-52 (3) ; 4759-56 (20) ; 4761-56 (11). 



A pair of conspicuous long palpi, seldom seen attached, have their 

 insertion in the groove between the prostomium and peristomium. The 

 details of the anterior end and neuropodial setae of the first segment 

 have been shown (Hartman, 1944, pi. 27, figs. 1-3). The modified setae 

 of abdominal segments are shown here (fig. 8). Length of the largest 

 posteriorly incomplete individual is 25 mm, with the thorax measuring 

 only about 5 mm long; the specimen has 9 thoracic and 4 abdominal 

 segments. 



Abdominal parapodia consist of low ridges nearly encircling the 

 body. The setae are in a double transverse row, with the posterior series 

 all slender and distally pointed. The anterior series are fewer in number, 

 broader in their distal parts, and terminating in a slender arista that is 

 continuous with the shaft ; they resemble subuluncini. A posterior end, 

 perhaps of this species, is present in the collection ; it consists of segments 

 that rapidly shorten and a pygidium with two pairs of short papillar 

 cirri. 



Distribution. — Longosoma catalinensis is known only from shallow 

 depths in outer or exposed areas of southern California; it is associated 

 with other polychaetes, Axiothella rubrocincta (Johnson) and Nephtys 

 ferruginea Hartman, and a cumacean, probably Diastylopsis tenuis 

 Zimmer, in very fine sand and silt, in temperatures of about 14.9° C. 





