256 



Annelida Chaetopoda 



and narrowed. In contraction this anterior part is about 

 equal in length to the posterior (f. 127) and is somewhat 

 shovel-shaped ; in extension it is double this length and is 

 acute, conical. A very shallow incision at the end can be 

 seen in alcoholic specimens; this was not noticed in living 

 forms. 



Eyes two, small, circular, lateral, posterior. 



Antenna, arises about the centre of the head, delicate, 

 subulate, in length not quite half the head. 



Dorsal ramus with dorsal cirrus but without proper feet 

 or ramus. Cirrus on first segment a mere papilla, increas- 

 ing in length to the fourth segment, where it is about 

 one-third the length of the branchiae ; the first three are 

 cylindrical; the fourth, and all back of it, on the bran- 

 chiated segments, have a small lobe, developed near the 

 base, looking outward. On the non-bran chiated posterior 

 segments this cirrus loses the lobe, becomes somewhat elon- 

 gated, very delicate, subulate. 



Ventral ramus, on first segment a minute cylindrical 

 papilla, a little longer than the dorsal cirrus; increasing 

 slightly in length to the fourth segment, where it is about 

 one-half as long as the dorsal cirrus. Back of the fourth 

 segment it is flattened (compressed) and becomes a fleshy 

 lobe, rounded externally. It retains this form to about 

 the 30th segment, where it again assumes the form of a 

 cirrus, shortens progressively, and disappears at about the 

 40th segment, after which segment the ventral rami are 

 entirely without appendages. The ventral cirri are always 

 just back of the ventral setae. 



Branchiae, begin on fourth segment, arise just within 

 the dorsal cirri, taper slightly to near the end when they 

 became suddenly acuminate ; they are usually directed 

 inward and a little upward, their length being a little more 

 than half the width of the body, so that they cross each 



