222 Introduction to Animal Morphology. 



hooks ; most are tube-dwellers, buried in sand or fastened 

 to stones ; body transparent ; eyes 2 (Disoma), or none. 

 17. Nerinidas — segments homonomous ; head with eyes; 

 feelers often none ; feet one- (Pygospio) or two-oared 

 (Nerine). Spio has tongue-like gills. Colobrachus has a 

 peculiar anal breathing organ. 18, Cirrhatulidae — rounded, 

 fusiform ; head with no teeth, feelers, nor tentacles ; oars in 

 two series, on the lower hooks; thread-like gills on five or 

 six anterior segments (Dodecaceraea), or on all but the first 

 and last (Cirrhatulus). Andoninia has spindle-like blood 

 corpuscles. 19. Ariciidae — with no feelers nor teeth, and 

 generally four eyes ; segments short ; oars two-branched. 

 The epipharynx is leaf-like in Anthostoma, protrusible in 

 Ephesia, which is eyeless, but not protrusible in the four- 

 eyed Sphserodorum. 20. Opheliidae — feelers and eyes none ; 

 zonites few ; oars small, one or two only with bristles, one 

 set of gills limited to the middle of the back (Ophelia), or on 

 nearly every segment (Travisia) ; head pointed ; tail papillary ; 

 body flat beneath, with (Ophelia) or without a definite " sole" 

 (Ammotrypane). Ophelia has in its perivisceral fluid stellate 

 bodies with immovable processes. 21. Arenicolidae — head 

 small, conical, with no eyes nor feelers, and a papillary pro- 

 boscis ; the middle segments have tree-like gills, while the 

 front and tail segments have none ; oars double, the upper 

 bristled, the lower hooked ; the larvae are polytrochal ; they 

 burrow in sand. Arenicola, the " lug-bait," has no tail ap- 

 pendages. Scalibregma has anal cirri. Eumenia has gills 

 on the anterior segments. 



4. Cephalobranchiata — mostly tube dwellers, with breath- 

 ing organs on the head, either as long contractile threads, or 

 fan-like, or spiral ; pinnate or comb-like lobes, and sometimes 

 tree-like gills on the prostomium ; some have dorsal cirri, 

 likewise respiratory ; no teeth nor epipharynx. i . Pherusidse — 

 free, and peristome bristle-less ; gills of simple threads, 

 surrounded by a girdle of long, yellow, thick bristles ; zonites 

 not ringed ; parapodia with upper linear and lower hook-like 

 bristles ; blood green ; body often shaggy, with sometimes 

 terminal suckers, whereby they adhere to foreign bodies 

 (Chlorsema Dujardinii is found adherent to Echini) ; intestine 



