[ 4 8 



irri with at mosl 27 (usually between 20 and 25) segments, short 



and stout; division series and arm bases well rounded dorsally, 



appearing narrow and only slightly flattened against tln-ir neigh- 



ours; 10 — 20 arms; division series 2 Kei Islands to southern 



la pan and the Hawaiian Islands) Parametra 



irri with more than |.o segments, long, slender or stout 

 e 1 division series and arms very narrow, slender, strongl) compres- 

 sed laterally, sharply carinate throughout; cirri very long and 

 verj slender: 20 arms; division series 2 (Kei Islands to the 

 Philip pines, and northward to southern Japan) . Stenometra 

 division series and arms usually stout, the latter well rounded 

 dorsally, at least in the earlier portion ; the ossicles of the 

 division series and the tirst two brachials are usually smooth 

 dorsally. but may have a very slight median keel, which is not 

 continued on to the arm bases 



f 1 IIBr series 4(3 + 4); division series and arm bases very 

 strongly rounded dorsally, the dorsal surface entirely free 

 of spinules or carinate processes (Bay of Biscay to the 

 Canaries and Ascension I si and; southern and 

 eastern A f r i c a t o the Moluccas and the Philip- 



pines) Crotalometra 



1 all division series 2; ossicles of the division series usually 

 with a flattened dorsal surface, perfectly smooth, with swollen 

 borders, or with a lateral, proximal and distal border of thickly 

 set fine spinelets (Caribbean Sea; sou th western 

 [ n d i a n Ocean to the Moluccas, the Philippines, 

 the Hawaiian Islands and southern Japan) . . Cosmiometra 



Crotalometra A. H. Clark. 



Key to the Species of the Genus Crotalometra. 



a 1 Centrodorsal thick discoidal, with the large stout cirri arranged in an irregular 



partially doublé row about the periphery 



li about 30 cirrus segments of which the longest are about twice as long as 

 broad; brachials from the first onward with the distal edges turned ontward 

 and produced, and the ossicles of the division series with the distal edges 

 prominent, giving the anima! a rugged appearance (Bay of Biscay to 

 the Canary Islands; 882- 1480 Metres flava 



b j.o 50 cirrus segments, the longesl only slightly longer than broad; division 

 series and arm bases nearly or quite smooth (Baj ol Biscay to As 

 cension I si and; 755 — [480 Metres porrecta 



