292 ANNELIDA 



lengili 10 cm. : Maine coast, from low-water mark to 30 fathoms, in rock 

 and sand; Europe. 



Family 9. ARICIIDAE. 



Usually cylindrical woims with short knob-like tentacles and palps, 

 or none at all, and with filiform gills which are more or less dorsal in 

 position: the worm forms a tube by cementing the sand around its 

 burrow, the position of which can be detected by a mound at the opening; 

 species not numerous. 



1. Aricia Savigny. Body short and composed of many small seg- 

 ments; tentacles and peristomial cirri absent; ventral cirri fimbriate or 

 pectinate: several species, 1 at Woods Hole. 



A. ornata Verrill. Body stout and somewhat flattened; gills flat- 

 tened, lanceolate, and begin on the sixth segment; length up to 26 cm.; 

 width 7 mm. : North Carolina to Cape Cod ; in shallow water. 



2. ScoLOPLOS Blainville. Body usually elongate and fragile, with- 

 out tentacles or peristomial cirri; proboscis lobulate: several species, 

 3 at Woods Hole. 



S. robustus (Verrill). Large worms 30 cm. long and 7 mm. wide, 

 with an acute head and small anterior parapodia; elongate gills begin 

 on segment 26; proboscis divided into about 18 long slender lobes; color 

 yellowish-brown : in shallow water, from North Carolina to Cape Cod. 



S. fragilis (Verr.). Body 12 em. long, 3 mm. wide; head acute, with 

 a 6-lobed proboscis; the gills begin to appear in segment 16; color yel- 

 lowish : between tide lines ; from North Carolina to Maine. 



Suborder 2. SPIONIFORMIA. 



Neither tentacles nor palps present; 1 pair of long peristomial cim 

 usually present; parapodia small, the dorsal cirri often large and form- 

 ing gills; proboscis without jaws; worms burrowing or tubicolous: 2 

 families. 



Family 1. SPIONIDAE. 



Small burrowing worms with a pair of long peristomial cirri which 

 usually curve over the back; dorsal cirri acting as gills; proboscis pres- 

 ent, but unarmed; body divided into 2 regions: in tubes in the sand, or 

 burrowing in wood or shells; species not numerous. 



Key to the genera of Spionidae here described. 



Ot Segment 5 not enlarged. 



6i Gills on hinder half of body 1. Spio 



^2 Gills absent on hinder half of body 2. Laonice 



O2 Fifth segment different from the others 3. Polydora 



