NOTES ON THE NAIDIFOEM OLIGOOH^TA. 355 



7. More than seventy-one segments, with a budding zone 



after segment xxii. 



8. More than seventy-eight segments, with a budding zone 



after segment xxii, and another budding zone after 

 the eighteenth segment beyond the new head of the 

 anterior budding zone. 

 I say " more than ^' so many segments in all these cases 



because it is impossible to count the actual number of segments 



in the tail region. 



P. inequalis, Ehrenberg, is insufficiently characterised, and 



P. flagellum, Leidy, does not belong, according to Vejdov- 



sky, to the genus Prist in a, but comes somewhere between 



Dero and Aulophorus. 



Naidium, O. Schmidt (see woodcut). 



One cephalized segment only recognisable in the fully grown 

 worm, and no information as to the bud. 

 There is no prostomial tentacle. 

 The dorsal setse are capillary and spear-shaped. 

 There are no branchial processes. 

 Eyes absent in the only known species. 



1. N. luteum, O. Schmidt. 



Chaetobranchus, mihi (see woodcut). 



One cephalized segment only, recognisable in the fully grown 

 worm, and insufficient information as to the bud. 



There is no prostomial tentacle. 



The dorsal setse are capillary and spear-shaped. Branchial 

 processes enclosing some or all of the setse of the dorsal bundles 

 present in all the anterior segments, with the exception of the 

 peristomial segment. 



In the shape and arrangement of the setae this genus very 

 closely approaches Naidium, from which genus it differs in 

 the remarkable branchial processes. 



1. C. semperi, mihi.^ 



' 'Quart. Journ. Micr. Sci.,' vol. xxxi, 1890. 



