ANNELIDS OF FAMILY NEREIDAE — HARTMAN 



475 



convex at both anterior and posterior margin and smooth except for 

 a few shallow grooves ; peristomial cirri short, the longest li/^ times 

 as long as peristomium, the shortest slightly over half as long as 

 the longest (fig. 50, a). 



Paragnaths dark brown, bluntly pointed cones to low round 

 plaques ; area I with three tiny teeth in a transverse row ; II with a 

 patch of 8 to 10 larger teeth ; III with a large lozenge-shaped patch 

 of many closely crowded teeth; IV with a small patch of a few 

 irregularly scattered teeth; V with none; VI with a tiny heap; 

 VII-VIII with a continuous band of several, irregular rows of 

 scattered cones. 



Figure 50. — Nereis (Nereis) natans, new species : o, "Head" and first 10 segments, 

 parapodia diagrammatically represented to show Increasing lengtlis of dorsal cirri and 

 return to normal cirri at ninth segment, X 26 ; 6, fourth parapodium, X 40 ; c, 

 eighth parapodium, X 40; d, thirteenth parapodium, X 40 ; e, natatory parapodium 

 from posterior three-fifths of body, X 40 ; /■, a posterior postnatatory parapodium in 

 posterior view, X SO ; g, right jaw in dorsal view, X 40 ; h, falcigerous heterogomph 

 neuroseta from prenatatory parapodium, X 333 ; i, falcigerous homogomph notoseta 

 from postnatatory parapodium', X 333. 



Jaws (fig. 50, g) amber brown, translucent, curved strongly in- 

 ward in distal half ; with four teeth on inner edge. 



Parapodia of segments 2-14 with lobes as in figure 50, h-d, and 

 setae of normal form; segments 15-39 with natatory parapodia 

 (fig. 50, e), those of segments 40-50 (fig. 50, /) similar to those 

 preceding segment 14; dorsal cirri of first seven setigerous seg- 

 ments gradually increasing in size (fig. 50, «) ; ventral cirri thickest 

 on first setigerous segment, gradually decreasing in size and becom- 

 ing normal at ninth segment; natatory parapodia about two-thirds 



