2 o6 DISCOVERY REPORTS 



with a serration along one edge; neuropodial chaetae are transparent and unidentate, beset with very 

 small spines; occasionally a superior chaeta in the neuropodial group may be bidentate. There is a 

 characteristic large caudal appendage terminating the body posteriorly. 



General distribution. Only one record of this species is known south of the Sub-Tropical Con- 

 vergence in the South Atlantic (see p. 259). 



The following species of Polynoinae were reported from the collections of ' Discovery ' by Monro 

 (1930) but have not been found in the present work. 



Nectochaeta caroli Fauvel, 1914 



Nectochaeta caroli Monro, 1930, p. 46, from St. 273, TYF, 200-23o(-o), 3 specimens; St. 276, N 100, ioo(-o) m., 

 29 specimens. 



Podarmus atlanticus Monro, 1930 



Podarmns atlanticus Monro, 1930, pp. 42-3, from St. 282 TYF, 30o(-o) m., 1 specimen. 



Stop-Bowitz (1948) reports this species from the North Atlantic and considers that Monro's 

 material could not have the forty-five segments described, if it had the fourteen pairs of elytra of the 

 original generic diagnosis by Chamberlin (1919). In fact, Monro's type (B.M.(N.H.), Reg. no. 

 1 930. 1 0.8.236), has forty-five chaetigers and eighteen pairs of elytrophores, as originally described. 

 Clearly the species is too little known to warrant accurate assessment, but it may represent 

 the pelagic phase of a benthic species. 



Sheila bathypelagica Monro, 1930 

 Sheila bathypelagica Monro, 1930, pp. 43-5, fig. 8, from St. 256, TYF, 850-1100 m., 1 specimen. 



Antinoe pelagica Monro, 1930 



Antinoepelagica Monro, 1930, pp. 63-5, fig. 16, from St. 45, NCS-T, 238-270 m., 1 specimen, and St. SS 18, 

 N 70 V, 50-0 m., 1 specimen. 



Macellicephala Mcintosh, 1885 



Macellicephala sp. Monro, 1930, St. 144, NCS-T, 155-178 m., 1 specimen. 



In 1936 Monro reported the following species from the collection of 'Discovery II': 



Harmothoe benthophila Ehlers, 1913 



Harmothoe benthophila Monro, 1936, pp. 87-8, from St. 702, TYFB, 236-0 m., 1 specimen. I have not found this 

 species in the present survey. 



ZOOGEOGRAPHY 

 1. Hydrological Environment 

 In the South Atlantic Ocean four hydrological zones can be recognized, the Antarctic, Sub-Antarctic, 

 Sub-Tropical and Tropical (Text-fig. 1, p. 165). Each zone has a characteristic surface water mass 

 beneath which are intermediate, deep and bottom water masses not confined by any surface zonation 

 (Text-fig. 14). 



It cannot be over-emphasized that neither the zones nor the water masses can be rigidly defined ; 

 they are subject to continual fluctuation and considerable intermixing. In the distribution maps, 

 therefore, their positions correspond as nearly as possible with conditions existing when the samples 

 were collected at the stations shown; in consequence these positions depart a little from the average 

 estimated from all available data by Deacon (1933, 1937) and Mackintosh (1946). 



