NO. 2 HARTMAN, BARNARD: BENTHIC FAUNA OF DEEP BASINS 137 



is biramous and resembles those of the following one. All have pointed 

 setae only, emerging in lateral series. In the first few segments the para- 

 podial ridges are at the midlength of the segment ; in the last several 

 thoracic segments, the ridges are gradually farther back. 



In larger individuals the first 5 thoracic segments are somewhat set 

 off from the next by being somewhat inflated. The thoracic formula may 

 be expressed as follows : 



Prostomium followed by an achaetous peristomium ; thoracic noto- 

 podia number 12 pairs with pointed setae only; thoracic neuropodia 

 number 1 1 pairs, with pointed setae. 



Long-handled hooded hooks are present in abdominal segments. Bran- 

 chiae are present in abdominal segments, perhaps not before the middle 

 region. At best development, they consist of 3 to 10-12 long, filiform, 

 non-retractile lobes in palmate arrangement, and emerge from the noto- 

 podial lobe, posterior to the uncinial ridge. An occasional filament is 

 bifurcated along its length. 



Leiochridcs is known for few species (see Hartman, 1947, p. 429) 

 from shallow sea bottoms. L. hcmipodus differs from others in that 

 abdominal segments have palmately divided branchiae. It is known only 

 from the basins of southern California and is presumed to be a deep 

 water form. 



Neoheteromastus, new genus 



Genotype : Neoheteromastus lineus, new species 



This genus is characterized by having a thorax consisting of 1 1 

 setigerous segments. The first segment or peristomium is a smooth ring. 

 This is followed by 8 segments in which notopodia have pointed setae 

 and 3 have uncini. The corresponding neuropodia include 6 with setae 

 and 4 with uncini. Abdominal segments have biramous parapodia pro- 

 vided with long handled hooks. 



Neoheteromastus differs from other capitellids having 1 1 thoracic 

 setigerous segments (Hartman, 1947, p. 402) as follows: Notomastus 

 Sars typically has only setae in the thorax and only hooks in the abdomen. 

 Mastobranchus Eisig has only setae in the thorax but the first 2 abdomi- 

 nal notopodia have setae and hooks. Heteromastus Eisig has 4 to 6 

 thoracic segments with setae, and 7 to 5 segments with hooks. Barantolla 

 Southern has 6 setigerous and 5 uncinigerous thoracic parapodia. In 

 Neoheterotnastus the thorax has notopodia of which 8 are setigerous and 



3 uncinigerous; the corresponding neuropodia include 6 setigerous and 



4 uncinigerous ; abdominal segments have only hooded hooks. 



