e 2 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 s 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 (Mar ion I s- 

 land, and the shores of the Antarctic continent in 

 the vicinity of Gaussberg; 252 — 400 Metres). . . . Eumorphometra 



Psathyrometra A. H. Clark. 



Key to the Species of the Genus Psathyrometra. 



a 1 Centrodorsal very long, much longer than broad, rounded conical ; very distinct, 

 though usually narrow, interradial lines running from the ends of the basal rays 

 to the apex 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 proximal pinnules increase in length and stoutness to P ;i , which 

 is longer and stouter than the two preceding pinnules 

 b 1 four columns of cirrus sockets in each radial area 



c 1 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, Japan; 540 — 959 Metres) .... fragilis 

 c 3 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 lar^e, and occasionally 

 there may be only three columns in some, very rarely in all, of the radial 

 areas ; cirri about 40 mm. long, composed of 22- -25 segments; arm length 

 about 80 mm. (sou theastern Alaska; 194 — 427 Metres). . . alascana 



b 3 three columns of cirrus sockets in each radial area 



c 1 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- — 355 1 



Metres) borealis 



c 3 smaller, arm length about 80 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 Alaska; 

 194 — 427 Metres) alascana 



