LEE BARKER WALTON 3 3 



G^. Capilliform setse only on one (6) or a few (6, 7, 

 8 ) segments. 



H^ Capilliform sets on segments 6, 7, and 8. 

 Prostomium developed into a tentacular process 



RJ pistes. 

 H-. Capilliform seta: only on segment 6. Pro- 

 stomium not developed into a tentacular process 



SLAVINA. 



F^. Length of capilliform sets shorter or rarely longer 

 than diameter of body. 



G^. Prostomium developed into a tentacular process 



STYLARIA. 



G". Prostomium rounded NAIS. 



C^. Dorsal bundle of sets beginning on segment 2. 



D^. Anterior capilliform sets partly covered by filamentous 

 gills Branchiodrilus. 



D^. No filamentous gills present. 



E^. Dorsal bundle usually composed entirely of capilliform 

 sets. Prostomium developed into a long tentacular 

 process PRISTINA. 



E~. Dorsal bundle composed in part of biuncinate or of 

 short needle-like sets. Prostomium rounded or with 

 a short tentacular process .... NAIDIUM. 



B^. Dorsal bundle of sets beginning on segment 12-20 Hoemonais. 

 Genus CHiETOGASTER K. Bacr, 1827 



Prostomium rudimentary, coalesced with segment 1; 

 2 ventral bundles of setae on a segment, these absent on 

 segments 1 and 3-5. Setze uncinate. Pharynx large and 

 wide. Esophagus small, not longer than pharynx; 1 pair 

 of transverse vessels connects the dorsal and the ventral 

 vessels. Longitudinal commissures of ventral nerve-cord 

 more or less distinct in anterior part of body. Testes in 

 segment 5, ovaries in segment 6, spermathec*E in seg- 

 ment 5. 



In fresh water, free-living or parasitic on fresh-water 

 snails. Middle and south Europe, North America. 



Five species are recognized by Michaelsen and to these 

 must be added C. pellucidus. Three species of Chsetogaster 

 (C. diastrophiis, C. diaphamts, and C. limnoei) have been 

 reported from North America, while Leidy ('52), de- 

 scribed C. gulosus, so incompletely, however, that it can- 



