322 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 10 



LONGOSOMA, new genus 



Type : L. catalinensis, new species 



Longosoma catalinensis, new species 



Plate 27, Figs. 1-3 



Collection.— 900-39 (1). 



An anterior end consisting of 9 thoracic setigerous segments and 3 

 greatly prolonged ones is 14 mm long. The prostomium is somewhat 

 depressed, tapers anteriorly but is broadly rounded in front, lacks eyespots 

 or other pigment marks. No appendages or indications of their bases can 

 be made out. The first segment is achaetous, apodous, biannulate (per- 

 haps represents 2 segments). This is followed by an anterior, thoracic 

 region of 9 setigers in which the rings are short, broad, with laterally 

 disposed setal fascicles. Long, cirriform tentacles, one pair to each seg- 

 ment, arise from the dorsal sides of the second to ninth setigers, totaling 

 8 pairs (pi. 27, fig. 1) ; they are slender, cylindrical, recall the lateral 

 tentacles of the cirratulids. This tentacular region is followed by one in 

 which the segments are very long; there are at least 3 such rings (posteri- 

 orly incomplete). Each of these rings is crossed by many, closely spaced, 

 transverse wrinkles, as though capable of great extension in life. The first 

 long segment is only about one third as long as the second, and the latter 

 is only about two thirds as long as the third. Each ring is surrounded, 

 dorsally and laterally, at its posterior margin, by fascicles of yellow setae, 

 that leave the ventrum plain. 



The proboscis is a smooth, soft sack, resembling that of the spionids ; 

 in the type it is everted (pi. 27, fig. 1). 



Parapodia of the first 9 pairs are lateral, notopodia and neuropodia 

 separated by a narrow, depressed gap; the upper ramus resembles the 

 lower one save that its fascicles are a little shorter, thinner, and it lacks 

 the short, thick, postsetal lobe which projects behind the neuropodial 

 fascicles of the first 8 setigers (pi. 27, fig. 1). Parapodia, posterior to this 

 region, are depressed, the fan-shaped fascicles seemingly project directly 

 from the body wall. Setae, so far as known, are entirely simple, smooth, 

 in very dense, transversely spreading fascicles. They are pale yellow, 

 slender, distally tapering, terminate in a fine point (pi. 27, fig. 3b). About 

 11 or 12 pairs in the posterior portion of the first neuropodium are longer, 

 thicker, end distally in a hook (pi. 27, fig. 3a). Setae of the prolonged 

 segments are somewhat finer, longer than those in front, and much more 

 numerous, but also simple, tapering, distally pointed. 



Holotype. — AHF no. 71. 



Type locality. — Off Long Point, Catalina Island, in 40 fms, from 

 brachiopod and sponge masses (coll. 900-39). 



Distribution. — Southern California. 



