NEREIS. 



157 



Hab. The coralline region. Apparently not unfrequent on the 

 Irish coast. Strangford Lough, and elsewhere on the coast of 

 Down, W. Thompson, Esq. ; Belfast Bay, JDr. Brummond. 



Desc. Body vermiform, flattish or rarely subcylindrical, as thick 

 as a goose-quill, only slightly tapered backwards, smooth, flat on the 

 ventral surface, which has the median line faintly impressed. Head 

 small, armed as usual (No. XXVIII.). Eyes very large. Jaws small, 

 with brown apices, serrated along the edge to the tip or nearly so. 



No. XXVIII. — Nereis Dumerilii. 



Tentacular cirri three times as long as the diameter of the post-occi- 

 pital segment, which is of about the same length as the next, and 

 rather narrower. Segments about eighty, narrowish, thickened above 

 the origins of the feet, which are well developed, and most crowded 

 on the posterior half of the body. Feet of the anterior segments (No. 

 XXIX. fig. 5) with three short obtuse branchial lobes, the dorsal one 

 more prominent than the others, and the setigerous tubercle minute : 



No. XXIX. — Nereis Dumerilii. 



of the middle and posterior feet (figs. 30 & 63) the branches are 

 widely remote, with the branchial lobes of the superior branch nearly 

 equal, divaricate, and a large brush of bristles between them. The 

 inferior lobe rather small and simple. Superior cirrus twice as long 



