e'- three columns of cirrus sockets in each radial area, the radial 
areas being separated by broad bare areas (Hawaiian 
Islands; 346 — 633 Metres) Sarametra 
d- size small; cirri with less than 30 segments; columns of cirrus 
sockets on the centrodorsal slightly irregular; interradial areas 
on the centrodorsal not especially differentiated (Marion Is- 
land, and the shores o f t h e Antarctic continent in 
the vicinity of Gaussberg; 252—400 Metresj. . . Eumorphometra 
Psathyrometra A. H. Clark. 
Key to the Species of the Genus Psathyrometra. 
a' Centrodorsal very lom.^-, much longer than broad, rounded conical; very distinct, 
though usually narrow, interradial lines running from the ends of the basal rays 
to the ape.x divide the sides of the centrodorsal into five radial areas, each of 
which contains three or four regular columns of cirrus sockets or from five to 
seven each; the pro.ximal pinnules increase in length and stoutness to P^, which 
is longer and stouter than the two preceding pinnules 
b' four columns of cirrus sockets in each radial area 
c' cirrus sockets very closely crowded, so that none of the lateral surface 
of the centrodorsal is visible between them; cirri about 45 mm. long, 
composed of 25 — 30 segments; arm length apparently about 100 mm., 
or rather more (Yezo Strait, Jajjan; 540—959 Metres) . . . . fragilis 
c- cirrus sockets not crowded and not in apposition with their neighbors, 
so that narrow bands representing the lateral surface of the centrodorsal 
are always visible between them ; sometimes the four columns of cirrus 
sockets in the radial areas alternate small and large, and occasionally 
there may be only three columns in some, ver)- rarely in all, of the radial 
areas; cirri about 40 mm. long, composed of 22--25 segments; arm length 
about 80 mm. (southeastern Alaska; 194 — 427 Metres). . . alascana 
b- three columns of cirrus sockets in each radial area 
c' larger, arm length about 130 mm.; cirri 55 mm. to 60 mm. long, com- 
posed of about 30 segments; cirrus sockets arranged in three regular 
columns, in contact longitudinally and usually also transversely (from 
Monterey. California, northward to the Shumagin Islands, 
and westward to the western Aleutian Islands; 1549 — 3551 
Metres) borealis 
c- smaller, arm length about So mm.; cirri about 40 mm. long, composed 
of 22 — 25 segments; cirrus sockets less crowded, rarely in contact, usually 
arranged in four columns in each radial area (southeastern .\laska; 
194—427 Metres) alascana 
