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characters of the former are— the prostomium is distinct 
and often bears, in addition to the paired eyes, sensory 
tentacles and palps (as, for example, in Verezs); the body 
segments are more or less alike and not divisible into two 
sharply-marked regions, distinguishable by the different 
arrangement and character of their setee and by internal 
differences. In the Cryptocephala the prostomium 1s 
compressed or hidden by forward growth of the peris- 
tomium and thus becomes insignificant; the tentacles are 
reduced but the palps become greatly enlarged and sub- 
divided, forming the crown of gills; the body is divisible 
into a “thorax” and ‘“ abdomen,” distinguished by the 
form and arrangement of their sete and by certain 
internal differences.  Arenicola belongs to the branch 
Phanerocephala which is divided into five sub-orders. 
I. Neremprrormr1a—Prostomial tentacles and palps 
well developed; pevistomial cirri usually present; para- 
podia well developed with acicula, dorsal and ventral 
eirr1; setve usually jointed; muscular pharynx with 
chitinous jaws; septa and nephridia regularly repeated 
throughout the body. Chiefly predaceous and carni- 
vorous worms, e.g., Vereds. 
Il. Sprronivormia._Prostomium without tentacles 
and palps; peristomium with a pair of long elrTl; para- 
podia project only to a shght extent, their dorsal cirr1 may 
be large and act as gills, sete unjointed ; no jaws; septa” 
and nephridia regularly repeated. Chiefly tubicolous or 
burrowing worms. 
III. Teresectirormia.—Prostomium forms a promi- 
nent lobe (upper lp) with or without tentacles, but with- 
out palps; peristomium may bear cirri or ‘ tentacular 
filaments’; parapodia feebly developed, ventral cirri 
absent, dorsal cirri may form gills, setee unjointed, uneini 
(short, sharply-curved dentate hooks) usually present; 
