BULLETIN 82, UNITED STATES NATIONAL MUSEUM 105 



with 18 joints, almost completely covering the centrodorsal. No syzygy on radials 

 [IBr series] or distichals [IIBr series]; the first on the third brachial. Colour bright 

 purple with lighter cirri. Macclesfield Bank, 22-30 fathoms." Bell assigned this 

 species to Carpenter's Spinifera group. It was named for Commander A. M. Field, 

 R. N., commanding officer of H. M. S. Egeria. 



I examined this specimen at the British Museum in 1910. There arc strong 

 transverse ridges on the cirrus segments. It is probably a species of Iconometra, pos- 

 sibly I. speciosa. 



Genus PETASOMETRA A. H. Clark 



Anledon (part) HARTLATJB, Nachr. Ges. Gottingen, May 1890, p. 174, and following authors. 



Cyllometra (part) A. H. CLARK, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 357. 



Petasometra A. H. CLARK, Smithsonian Misc. Coll., vol. 60, No. 10, 1912, p. 25 (diagnosis; genotype 

 Anledon clarae Hartlaub, 1890; assigned to the family Colobometridae; comparisons); Die 

 Fauna Siidwest-Australians, vol. 4, Lief. 6, 1913, p. 311 (detailed description and comparisons; 

 genotype; Shark Bay to Amboina) ; Journ. Washington Acad. Sci., vol. 5, No. 1, 1915, p. 8 (very 

 highly developed in the Australian fauna); Unstalked crinoids of the Siboga Exped., 1918, pp. 

 Ill, 112 (in key), p. 113 (key to the included species). GISL&N, Kungl. Fysiogr. Sallsk. Handl., 

 new ser., vol. 45, No. 11, 1934, pp. 20, 22, 23, 27; Kungl. Fysiogr. Sallsk. Lund Forh., vol. 7, 

 No. 1, 1936, pp. 2, 17. H. L. CLARK, Echinoderm fauna of Australia, 1946, p. 48 (in key), 

 p. 51 (key to the included species). 



Diagnosis. A genus of Colobometridae including medium-sized species with 

 10-22 arms 85-120 mm. long, with the IIBr and IIIBr series (when present) 4(3+4), 

 rarely 2; PI and P 2 are similar, somewhat enlarged and evenly tapering, with 22-24 

 segments, longer and stronger than P 3 ; P a is absent; there are 19-31 cirrus segments, all 

 much broader than long. 



This genus is distinguished from Cyllometra by having PI and P 2 similar, by having 

 the IIBr and IIIBr series usually 4(3+4), and by the larger size. 



Geographical range. From Flores to Amboina and Darwin, Australia, and south- 

 ward to Shark Bay, Western Australia. 



Bathymetrical range. From the short line down to 40 meters. 



History. The genus Petasomelra was established by me in 1912 with the genotype 

 Antedon clarae Hartlaub, 1912, a species which since 1907 had been assigned to the 

 genus Cyllometra. At the same tune a second species, P. helianthoides, was described. 



KEY TO THE SPECIES IN THE GENUS PETASOMETRA 



a 1 . More than 20 arms; 28-31 cirrus segments (Shark Bay, Western Australia, to Darwin, Northern 

 Territory; 0-9 meters).- - helianthoides (p. 105) 



a 2 . Arms 10-14 in number; 20-29 (usually 20-25) cirrus segments (Amboina and Flores; 0-40 

 meters) - clarae (p. 109) 



PETASOMETRA HELIANTHOIDES A. H. Clark 



Petasomelra helianthoides A. H. CLARK, Smithsonian Misc. Coll., vol. 60, No. 10, 1912, p. 26 (descrip- 

 tion and comparisons; South Passage, Shark Bay, 9 m.) ; Die Fauna Sudwest-Australicns, vol. 4, 

 Lief. 6, 1913, p. 311 (description; same locality), pi. 4, fig. 4 (dorsal view), fig. 5 (ventral view); 

 Rec. Western Australian Mus., vol. 1, pt. 3, 1914, p. 114 (already recorded from Shark Bay); 

 Internat. Rev. gesamt. Hydrobiol. und Hydrogr., 1915, p. 224 and following (detailed account 

 of the distribution in Australia). H. L. CLARK, Biol. Results Fishing Exper. F. I. S. Endeavor, 

 1909-14, vol. 4, pt. 1, 1916, p. 6 (characteristic of the west Australian subregion). A. H. CLARK, 

 Unstalked crinoids of the Siboga-Exped., 1918, p. 1 13 (in key; range). GisLtfx, Kungl. Fysiogr. 

 Sallsk. Handl., new ser., vol. 45, No. 11, 1934, pp. 22, 27. H. L. CLARK, Kchinoderm fauna of 

 Australia, 1946, p. 51. 

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