140 
Cunha; Socotra to South Africa and the Ci'ozet 
Islands, and eastward to tlie Kerniadec, Galapagos, 
Hawaiian and western Aleutian Islands, and southern 
Japan; littoral, and down to 2926 Metres) Th al asso me t r i n ae 
1=*' Subfamil\- P t il o m e t r i n a e A. H. Clark. 
Key to the Genera of the Subfamily Ptilometrinae. 
a' Centrodorsal large and broad, thick discoidal or columnal, the numerous cirri 
closely crowded and irregularly distributed, though tending to arrange them- 
selves in fifteen columns; the radial areas of the centrodorsal are never 
differentiated (southwestern, southern, and southeastern Australia) Ptilometra 
a- Centrodorsal a short, more or less pentagonal, column, with a conical apex; 
the comparatively few cirri are arranged in ten definite columns, two to each 
radial area; the radial areas are separated from each other by more or less 
developed ridges 
b^ 10 — 13 arms; the pinnules in the proximal third of the arm are much 
shorter than those in the distal half, and are composed of segments 
which, except occasionally at the extreme tip, do not have overlapping 
and spinous distal ends ; the longer proximal cirrus segments have 
approximately straight ventral and dorsal borders (as viewed laterally) 
which are usually parallel, though they may diverge very slightly distally; 
there is no central constriction, or production of the distal edge (Lesser 
Sunda Islands to southwestern Japan) Asterometra 
b- 20 — 30 arms; the pinnules in the proximal third of the arm are gis 
long as, or even longer than, those in the distal half, and are composed 
of segments many or most of which are constricted centrally with 
produced and spinous distal ends; the longer proximal cirrus segments 
are usually more or less constricted centrally with prominent distal ends 
the ventral border of which usually more or less overlaps the base of 
the succeeding segment, and may be produced into a long ventral spine 
(Gulf of M a r t a b a n to northern Celebes and the Philip- 
pine Islands) . . Pterometra 
Asterometra A. H. Clark. 
Key to the Species of the Genus Asterometra. 
a' Elements of the IBr series and first two brachials without prominent median 
keels or tubercles 
b' centrodorsal small and conical (Formosa) . . . lepida 
b" centrodorsal large, columnar, with a conical apex 
