NO. 2 HARTMAN, BARNARD: BENTHIC FAUNA OF DEEP BASINS 130 



between thorax and abdomen is not sharp but is distinguishable by a 

 difference in parapodial components. The prostomium is a small, semi- 

 circular lobe without eyes. It is followed by a smooth peristomial ring. 

 The first 6 setigerous segments have setae in both notopodia and neuro- 

 podia. They are followed by 4 segments having long handled hooks in 

 both rami. The thoracic epithelium is smooth and glistening throughout. 



Abdominal segments have long handled hooks; they differ also from 

 those in the thorax in that the epithelium is thinner and flaccid. In far 

 posterior segments the notopodia have a short, digitate lobe a little longer 

 than wide, directed dorsolaterally; there is one pair to each segment; 

 these lobes may be branchial but are not eversible. 



Mediomastus glabrus differs from the only other known species of 

 the genus, M. calif or niensis Hartman (1947, p. 407), in that the latter 

 has setigerous segments 2 to 5 with pointed setae and 6 to 1 1 with long 

 handled hooks. The latter is very common in shallow depths in fine sedi- 

 ments (unpublished data) ; M. glabrus is a deep water form. 



Genus NOTOMASTUS Sars, 1851 



Notomastus magnus Hartman, 1947 

 Hartman, 1947, pp. 412-415, pi. 50, figs. 1-6. 



An immature or vegetative specimen from East Cortes Basin is ques- 

 tionably referred to this species. It is known more extensively from inter- 

 tidal and shallow depths of California. 



Notomastus precocis, new species 



The type is selected from Santa Catalina Basin (Sta. 2848) ; other 

 specimens come from San Pedro, Santa Catalina, Tanner and Long 

 Basins. Length of a larger individual is 15.5 mm; width in the thorax 

 or widest part is 1.2 mm; number of segments exceeds 50. The prosto- 

 mium is a short, equally triangular lobe and lacks eyespots. The thoracic 

 epithelium is smooth ; its parapodial lobes are inconspicuous and occur 

 at the midlength of the segments. The first segment or peristomium is a 

 smooth, slightly biannulated, complete ring lacking parapodia. The next 

 segment is complete with notopodia and neuropodia. 



The everted proboscis is globular and proximally covered with coarse, 

 triangular papillae. In the thorax, the notopodia have only pointed setae; 

 neuropodia have setae in the first 8 segments and long handled hooks in 

 the last 3 segments. Abdominal segments have only long handled hooded 



