216 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 7 



5. Posterior notopodia with homogomph falcigerous setae; noto- 

 podial preacicular lobe not elongate . . . NEREIS, p. 220 



5. Posterior notopodia without falcigerous setae; some notopodial 

 preacicular lobes elongate, especially in a posterior region . . 

 NEANTHES, p. 219 



6. Proboscidial areas I, II, and V with paragnaths; area VI with 

 transverse plaques ; homogomph falcigerous setae absent . . . 

 PSEUDONEREIS, p. 231 



6. Proboscidial areas I, II, and V lack paragnaths, area VI with 

 points ; some notopodia with falcigerous setae 7 



7. Posterior notopodia with simple, stout, falcigerous setae . . . 

 UNCINEREIS, p.231 



7. Posterior notopodia with composite, stout, falcigerous setae (pi. 

 38, fig. 83) PLATYNEREIS, p. 229 



Genus LEPTONEREIS Kinberg* 



Proboscis lacks chitinous paragnaths. Jaws pale, translucent, with ob- 

 lique teeth on the cutting edge. Parapodia with heterogomph and homo- 

 gomph spinigerous setae; neuropodia with heterogomph falcigerous setae. 

 Notopodia without homogomph falcigerous setae. Epitokous forms with 

 2 or 3 body regions, an anterior and sometimes a posterior region with 

 atokal setae, and a median region with natatory setae. 



Kinberg (1866, pp. 178-179) erected 3 genera, Leptonereis, Nicon, 

 and Nicomedes. Most of the species therein named have since been in- 

 cluded under heptonereis. Nicon and Nicomedes, in part at least, are epit- 

 okous stages of heptonereis species. The following were described from 

 the eastern Pacific: Nicon loxechini and A^. virgini from the Straits of 

 Magellan, Leptonereis laevis from Guayaquil, and Nicon tahitanus from 

 Hawaii. Unfortunately, most of these are too incompletely known to per- 

 mit identity. 



The collections at hand include numerous specimens of pelagic epit- 

 okous stages. They differ greatly among themselves as to number of an- 

 terior, atokal segments, and comparative sizes. Until more is known about 

 the sedentary stages from which these are derived, it has been deemed 

 best to postpone the description of them until additional material is avail- 

 able. The one described below has been based on material which permits 

 a more complete diagnosis. 



* The types of Leptonereis, Nicoii and Nicomedes have been reexamined, ne- 

 cessitating important changes in these genera. They are to appear in a subsequent 

 revision of some Swedish types. 



