CLARK] NEW GENERA OF RECENT FREE CRINOIDS 351 



The following are the described species of the genus : 



Heliometra antarctica (P. H. Car- H eliometra magellanica (Bell) 



penter) maris (A. H. Clark) 



asperrima (A. H. Clark) maxima (A. H. Clark) 



brachymcra (A. H. Clark) " perplexa (A. H. Clark) 



clio (A. H. Clark) quadrate (P. H. Carpen- 



" eschrichtii (J. Muller) ter) 



glabra (A. H. Clark) 1 " rathbuni (A. H. Clark) 



liondoensis (A. H. Clark J rhomboidea (P. H. Car- 



incxpectata (A. H. Clark) penter) 



juvenalis A. H. Clark serratissima (A. H. Clark) 



laodice (A. H. Clark) tanneri (Hartlaub) 



5. THYSANOMETRA, gen. nov. 



Centro-dorsal discoidal, bearing 50 to 70 marginal cirri in several 

 marginal rows; cirri slender and very smooth, with 15 to 20 greatly 

 elongated segments ; no trace of dorsal spines ; no opposing spine ; 

 terminal claw very long and nearly straight ; disk and ambulacra 

 naked ; costals rounded, well separated, never carinate ; ten arms, the 

 brachials mostly oblong, but sometimes slightly quadrate in the 

 anterior third of the arm ; third and fourth, ninth and tenth, and 

 fourteenth and fifteenth brachials united by syzygy; syzygia distally 

 with usually 3 bifascial articulations intervening; lower pinnules 

 greatly elongate and flagellate, the first composed of very numerous 

 short and broad segments, the others of segments all but the basal 

 3 or 4 of which are greatly elongated ; distal pinnules very slender, 

 with greatly elongated segments. 



Color in life grayish brown, the skeleton and cirri nearly white. 



Type of the genus. — Antedon tenclloides A. H. Clark, 1907. 



This genus contains a single peculiar species, known only from 

 southern Japan. It is : 



Thysanometra tenelloides (A. H. Clark) 



6. ANTEDON de Freminville 1811 



Centro-dorsal hemispherical, rarely more or less discoidal, bearing 

 from 10 to 15 to nearly 60 cirri, the pole always free ; cirri of variable 

 length, composed of from 10 to 50 segments, all of which are usually 

 longer than wide (frequently very much so) ; although the last few 

 are sometimes comparatively short, there is never any great differ- 

 ence between the longest and the shortest segments ; cirrus segments 



1 Heliometra glabra, new name for Antedon aus traits P. H. Carpenter, 1888; 

 not Antedon australis P. H. Carpenter, 1882. 



