278 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



no jaws; septa incomplete except one strong diaphragm 

 in front ; anterior to this the nephridia are large and 

 excretory while the posterior ones are mere funnels and 

 act as genital ducts. Tubicolous or burrowing worms. 



IV. Capitellieormia. — No prostomial processes ; 

 parapodia do not project, seta? unjointed, capilliform in 

 the anterior segments, hooded crotchets in the posterior 

 segments (this division does not correspond to marked in- 

 ternal differences), no cirri; no jaws; nephridia small and 

 may be more than one pair per segment ; no blood-vessels, 

 but the coelomic corpuscles are red. Burro wers. 



V. Scoleciformia. — Prostomium rarely with sensory 

 processes ; peristomium without cirri ; parapodia not well- 

 developed, setse unjointed, no uncini present; no jaws; 

 septa not regularly developed (some being absent) ; 

 nephridia often reduced in number but all alike. 

 Burrowers. 



Arenicola belongs to the last sub-order, which contains 

 six families. 



(1) Opheliid^e. — Comparatively short worms, many 

 of which have a pearly lustre ; no prostomial processes ; 

 parapodia obscure, but dorsal cirri often present, e.g., 

 Ophelia. 



(2) Maldanid^e (or Clymenid^e). — Prostomium 

 truncated ; body formed of long and few segments, never 

 provided with gills or other processes ; the neuropodial 

 setse are hooked crotchets, each with characteristic sub- 

 rostral tuft. Inhabit sandy tubes, e.g., Nicomache, 

 Axiothea, Clymene. 



(3) Arenicolid^e. — See below for definition. 



(4) Scalibregmid^e. — Arenicoliform or maggot like; 

 gills, if present, confined to the first five segments ; pro- 

 stomium small and either drawn out at its lateral angles 

 into short processes or bluntly rounded ; parapodia con- 



