ZOOGEOGRAPHICAL REVIEW 26 3 



8. The following species have been found only to the north of the Sub-Tropical Convergence. It 

 is evident that most of them, and probable that all of them, are limited to the south by this boundary 

 though the evidence is not conclusive for some of the scarcer species : Tomopteris ligulata, T. krampi, 

 T. elegans, T. apsteini, T. nisseni, Vanadis formosa, V. crystallina, Rhynchonerella angelini, Krohnia 

 lepidota, Alciopa reynandii, Naiades cantrainii, Travisiopsis lobifera, T. lanceolata, Lopadorhynchusbrevis, 

 L. uncinatus, L. krohnii. 



All these species have also been reported from the North Atlantic Ocean, where the majority of them 

 appear to be restricted in their northerly distribution by a surface hydrological boundary, the Secondary 

 Polar Front or Labrador Front (Bohnecke, 1938), approximating to the Sub-Tropical Convergence in 

 the South Atlantic. Bohnecke distinguished the Secondary Polar Front by a temperature of 15 C. in 

 summer and 9 C. in winter, extending along the cold-wall region in the left bank of the Gulf Stream 

 to approximately 53 N. in 30 W. To the east of this position, around the British Isles and North- 

 west Europe, the disposition of the land masses makes it difficult to distinguish a convergence. 1 



Collections from the North Atlantic Ocean have not been available in quantity for examination, but 

 in addition to the material in the British Museum (Nat. Hist.) reported by Monro (1939 a), I have 

 consulted the work of the following authors, who have recorded pelagic polychaetes from near the 

 Secondary Polar Front and/or north of it about the Polar Front: Reibisch (1895), Apstein (1900), 

 Huntsman (1921), Wesenberg-Lund (1935, 1936), Treadwell (1943, 1948), Stop-Bowitz (1948), 

 Wesenberg-Lund (19506, 1953), Grainger (1954). 



In these references I can find no record of the following species from north of the Secondary Polar 

 Front in the North Atlantic Ocean: Tomopteris ligulata, T. elegans, T. apsteini, Vanadis formosa, 

 V. crystallina, Krohnia lepidota, Alciopa reynaudii, Naiades cantrainii, Travisiopsis lobifera, Lopado- 

 rhynchus uncinatus, L. brevis, L. krohnii. 



The water circulation in the North Atlantic Ocean is much more complicated than south of the 

 Equator, but although I have made no attempt to interpret distribution in depth, it is significant that 

 these species are restricted by somewhat similar surface hydrological conditions to those which limit 

 their movement in the South Atlantic Ocean. 



The remaining species, Tomopteris nisseni, T. krampi, Rhynchonerella angelini, and Travisiopsis 

 lanceolata range northwards beyond the Secondary Polar Front in the North Atlantic Ocean— in brief 

 this front is no barrier to them. No endemic pelagic polychaetes are known from arctic waters, which 

 implies that there is a constant influx of more southerly populations maintaining the homogeneity of 

 the species over a wide area and preventing the evolution of endemic forms. It is possible therefore 

 that the endemic antarctic Tomopteris carpenteri may be represented in the arctic fauna by T. nisseni 

 and T. krampi. Similarly the endemic antarctic Rhynchonerella bongraini corresponds to R. angelini. 

 Likewise, although the genus Travisiopsis is not represented by an endemic species in the Antarctic 

 Zone the species T. coniceps occurs only in southern waters and its corresponding species in arctic 



waters is T. lanceolata. 



9. The following species were collected in all hydrological zones in the South Atlantic Ocean: 

 Tomopteris planktonis, T. septentrionalis, Typhloscolex mulleri, Travisiopsis levinseni, Pelagobia longi- 



cirrata. 



Of these, Tomopteris planktonis, T. septentrionalis and Travisiopsis levinseni were collected in all 

 explored water masses but never in abundance. Many more samples are needed before their dis- 

 tribution can be accurately analysed. 



1 East of 53 N 30 W., where no clear boundary can be distinguished, Southern (191 1) has reported Vanadis formosa 

 from stations with 'surface temperatures between iz° and 16-3° C. and Alciopa reynaudii as Greefia celox from stations with 

 surface temperatures between 10-5 to 11-15° C. 



