731 



THE RECENT CRINOIDS OF AUSTRALIA — CLARK. G87 



a". More than ten (usually 15-20) arms ; cirri irregularly arranged, 

 or arranged in fifteen closely crowded columns, an a large 

 columnar centrodorsal ; P^ smaller than P, Ptilometra. 



Key to the Genera of the Himerometrid.e. 

 a^. Distal brachials exceedingly short and discoidal ; arm bases very 



rugged Amphimetra. 



a"^. Distal brachials wedge shaped and not especially short ; arm 

 bases smooth. 

 61. II Br 4 (3 + 4). 



c^. Cirri long, stout basally but gradually tapering to a point 



distally Craspedometra. 



c^. Cirri moderate, nottapering distally Heteromelra. 



The following Families are represexted in Au.stralian Seas by but 

 A SINGLE Genus each. 

 Zygometridaj ; Tropiometridse; ^Stephanometrid8e; Mariametridi* ; and 

 Antedonidje. 



Key to the Genera of Australian Crinoids co>taining Species with 



ten arms only. 

 a^. Lower pinnules provided with a terminal comb ; mouth excentric, 



anus central or nearly so Comatula. 



a^. Lower pinnules without terminal combs ; mouth central, arms 

 marginal. 

 6*. Pa absent. 



c^. All the pinnules very stilT ; cirri long, with more than 



forty segments Golobometra. 



c^. Only Pg stiffened ; cirri short, with less than twenty seg- 

 ments Decametra. 



b^. Pa present. 



c^. All the pinnules sharply triangular, the first much en- 

 larged Stiremetra. 



c''. All, or at least the distal pinnules, cylindrical. 



d^. Pj twice as long as Pj Gompsometra. 



d2. Pj^ shorter than P^. 



e^. The lower pinnules bear stout processes on the seg- 

 ments Oligometra. 



e'^. The lower pinnules do not bear processes on the 

 segments. 

 /I. Cirri slightly tapering distally, rather slender, 

 with processes on the dorsal side of tlie distal 



segments A mphiinetra. 



p. Cirri stout and smooth, not tapering distally 



Tropiometru . 



Key to the Genera of Australian Crinoids containing Species with 

 more than ten arms, whose division series are all of two ossicles 

 each. 

 a'. The proximal pinnules bear terminal combs ; mouth marginal or 

 submarginal ; anus more or less central, 

 fei. Cirri absent ; elements of division series apparently united by 



syzygy Comatula. 



