3''^ Subfamily Zenometrinae A. H. Clark. 
Key to the Genera of the Subfamily Zenometrinae. 
a^ P, and P^ absent (Philippine Islands; 140 — 14S Metres) . . . Balanometra 
a- P, and P^ present 
b' cirri with all the segments elongated, the distal entirely without dorsal 
processes -, or (very rarely) a few of the outermost cirrus segments may 
be but little longer than broad with slight dorsal tubercles 
c^ cirrus sockets arranged in closely crowded columns in each radial 
area; but the groups of columns in each radial area are usually 
(almost invariably) separated from the groups of columns in the 
adjacent radial areas by long-triangular bare patches; the distal 
cirrus segments are always greatly elongated, never with any trace 
of dorsal processes (from the Galapagos Islands and Pa- 
n a m (i northward to the Aleutian Islands, and south- 
ward on the Asiatic coast to Yezo Strait and the 
northern ji a r t of the Sea of Japan; the Hawaiian 
Islands; the Philippine Islands; the lesser S u n d a Is- 
lands; the Bay of Bengal and the coast of Travancore, 
and southward to the Antarctic regions; 336 — 2858 
Metres) Psathyrometra 
c" columns of cirrus sockets somewhat irregular, and evenly spaced all 
around the centrodorsal without differentiation into radial groups ; 
the distal cirrus segments may be much elongated with no trace 
of dorsal processes, or little, if any, longer than broad, with slight 
dorsal tubercles (from the western coast of .Scotland, and 
Ireland, southward to Madeira, including the entire 
Mediterranean basin; 45 — 1292 Metres) Leptometra 
b- cirri with the -proximal segments more or less elongated, but the 
distal segments short, never longer than broad, and bearing prominent 
dorsal processes 
c^ division series and arm bases smooth; 10 — 14 arms (Kei Islands 
and northern Cuba; 252 — 380 Metres) Adelometra 
c" division series and arm bases spiny 
d^ size large; cirri with more than 40 (50 — 60) segments; columns 
of cirrus sockets very regular, separated interradially by high 
ridges, or by broad bare areas 
e' two columns of cirrus sockets in each radial area, the radial 
areas being separated by high ridges (from St. Lucia, 
British West Indies, northward to Georgia and 
Pensacola, F 1 o r i d a ; 304 — 792 ^Metres) Zenometra 
