32 EOHTNODERMS OF THE BRITISH ISLES 



species, A. bifida, is likely to prefer shallower water, at least on 

 the southern coasts of Great Britain. 



Subfamily Zenometrin^ 

 2. Poliometra A. H. Clark*. 



Centro-dorsal conical with cirrus-sockets arranged, more or 

 less distinctly-, in vertical columns. Segments of the cirri longer 

 than broad, swollen at the articulations, but not with very 

 prominent dorsal processes. Brachials smooth, without promi- 

 nent spines on the distal edge. Pinnule^ much elongated, usually 

 ca. 3 times as long as P2. 



Only one species in European seas (the only species known 

 of the genus). 



1. Poliometra prolixa {Sladen). (Fig. 18.) 

 (Syn. Antedon, Hathrometra prolixa Sladen.) 



Cirri ca. Ix-lxx, with ca. 40 segments, very long and slender, 

 ca. 4 times as long as broad in the middle of the cirrus. The 



Fig. 18. — Poliometra prolixa. Nat. size. (From Th. Mortensen, Eclmiod. 

 N.E. Greenland.) 



terminal joint forms a delicate hook, and there is a fairly distinct 

 opposing spine on the penultimate joint. The first pinnule has 



