346 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



The relations between Amphimetra and Heterometra were therefore reexamined, 

 and in my report on the unstalked crinoids of the Siboga expedition published in 1918 

 1 restricted the genus Amphimetra 90 as to include only spectabilis (here mentioned for 

 llu- lirst time), moUeri, parilis, jacquinoti, pinniformis, discoidea, ensifer, laevipinna, 

 and papuensis. Except for the inclusion of panhs, herein referred to Heterometra, 

 Amphimetra was given the same status as in the present volume, and only 10-armed 

 species were assigned to it. A new genus, Homalometra, was established for Antedon 

 denticulate P. H. Carpenter, 1888, previously referred to Amphimetra. No revised 

 diagnosis of the genus Amphimetra was published, but the scope of the genus, and also 

 of Heterometra, was made clear by keys to the included species. The complete 

 synonymy of all the species of Amphimetra was given, and the distribution of each was 

 given in detail. In addition to the nine species given above, three (milberti, sinensis 

 [Antedon sinensis llartlaub, 1912], and tessellata) were listed as doubtful species, as 

 at the time their relationships could not be satisfactorily determined. 



In 1919 Dr. Torsten Gisl6n discussed the relationship between variipinna and 

 crenulata and also that between milberti and discoidea, uniting them into variipinna 

 and milberti, respectively. He also discussed the relationship of schlegelii with the last. 

 All these forms he referred to Amphimetra, his paper having been written before he 

 had seen the Siboga report. 



KEY TO THE SPECIES AND SUBSPECIES OF THE GENUS AMPHIMETRA 



a 1 . Cirri very stout, composed of short subequal segments, which are never more than half as 

 long as broad; segments in outer portion of cirri are very slightly longer than those in prox- 

 imal portion and bear small sharp median spines; cirri are very flexible and are more or less 

 evenly curved throughout their entire length. 

 fc 1 . Size large, arms 200 mm. long; cirri large and stout with 45-51 segments, most of which are 

 about 4 times as broad as long; dorsal spines are developed from usually the sixteenth or 



seventeerth segment onward (Philippine Islands; 0-64 meters) spectabilis (p. 347) 



V. Smaller, arms not over 150 mm. long; cirri with 24-50 segments, which are 2-3 times as broad 

 as long; dorsal spines are developed before eighth segment. 

 c 1 . Larger, arms 75-150 mm. long; cirri with usually 30-35 segments; F 2 with 18-21 segments 



(Maldive Islands to Philippines; 0-55 [?66] meters) molleri (p. 349) 



c?. Smaller, arms about 60 mm. long; cirri with 25 segments; P 2 with 12 segments (New Guinea 



and northwestern Australia; 0-27 meters) pinniformis (p. 358) 



a*, i irri less stout, segments in proximal half varying from nearly twice as broad as long to 



slightly longer than broad, segments in distal half (except for a few terminal) shorter, always 



much broader than long; cirri more or less stiffened in proximal portion though flexible distally, 



so that they are strongly curved distally but much less curved proximally. 



6 1 . Longest cirrus segments usually half again as broad as long, but varying from nearly twice as 



broad as long to nearly as long as broad; cirri with 35-47 segments, 30-50 mm. long; earlier 



segments sometimes with a broad transverse ridge or paired spines; arms 130-300 (usually 



150-200) mm. long, usually 10, but occasionally 11-12, with the IIBr series 2; color uniform 



dark purple or violet (Sunda Straits to Moluccas and Kei Islands and southward to Port 



Molle, Queensland, and to between Fremantle and Geraldton, Western Australia; 0-109 



?[183] meters) tessellata tessellata (p. 360) 



f. Longest cirrus segments about as long as broad. 



<■'. S\ -narthrial tubercles not extravagantly developed, though they may be prominent. 



d l . Larger, arms 110-200 mm. long; 34-51 cirrus segments of which the outer bear short dorsal 

 spines or pointed tubercles; synarthrial tubercles prominent and sharp pointed (Formosa 

 and Philippine Islands to Singapore and southward to Port Molle, Queensland, and 

 llolothuria Bank, northwestern Australia; 0-93 meters). .tessellata discoidea (p. 376) 



