A MONOGRAPH OF THE EXISTING CRINOIDS 417 



Foren. K0benhavn, 1909, p. 193 (probably occurs at Singapore); Die Fauna SiidwestrAustraliens, 

 vol. 3, Lief. 13, 1911, p. 439 (closely related to Ptilometra which represents it in Australia); 

 Mem. Australian Mus., vol. 4, 1911, p. 725 (absent from Australia), p. 728 (referred to the 

 Thalassometridae) ; Crinoids of the Indian Ocean, 1912, p. 9 (absent from Australia), p. 10 

 (absent from Japan; reason), p. 11 (represented in the Ceylon region, its western limit), p. 24 

 (range; represents Ptilomelra), p. 42 (referred to the Thalassometridae), p. 59 (in key), p. 189 

 (oiiginal reference; type) ; Unstalked crinoids of the Siboga-E\pod., 1918, p. 14 (in key; range), 

 p. 143 (key to the included species). GISLEN, Nova Acta Reg. Soc. Sci. Upsaliensis, ser. 4, 

 vol. 5, No. 6, 1922, p. 99; Zool. Bidrag Uppsala, vol. 9, 1924, p. 231. SIEVEBTS, Neues Jahrb. 

 Min., Geol. und Pal., vol. 69, Beilage-Band, Abt. B, 1932, pp. 151, 156. EKMAN, Tiergeographie 

 des Meeres, 1935, p. 283. 



Diagnosis. A genus of Asterometridae in which the arms in fully developed 

 individuals are 20-30 in number; the pinnules in the proximal third of the arm are as 

 long as, or longer than, those in the distal half and are composed of segments many 

 or .most of which are constricted centrally with produced and spinous distal ends; 

 the longer proximal cirrus segments are usually more or less constricted centrally with 

 prominent distal ends which on the ventral side usually more or less overlap the bases 

 of the segments succeeding and may be produced into a long spine. 



Geographical range. From the Kei Islands and eastern Java northwestward to 

 the Gulf of Martaban and northward to Cochin China, the Philippines, and the 

 Benin Islands. 



Bathymetrical range. From 5 to 106 (?183) meters; most frequently reported 

 between 50 and 100 meters. 



Thermal range. One record, 24.28 C. 



Remarks. The species of this genus are of very characteristic appearance. 

 They are easily distinguished from the species of Ptilometra by the smaller centro- 

 dorsal on which the cirri are arranged in ten definite columns, and from the species 

 of Asterometra by the greater number of arms and also by their color, the species of 

 Pterometra being mostly red, purple, or brown, uniform or striped or blotched with 

 light, whereas the species of Asterometra are usually clear light yellow. The specific 

 limits recognized within the genus are to a certain extent tentative as few are known 

 from a sufficient number of individuals to indicate adequately the range of variations. 



History. The first known species of this genus was described under the name of 

 Ptilometra trichopoda in 1908. In 1909 this species was made the type of the new 

 genus Pterometra. In 1911 Asterometra magnipeda was described, which was trans- 

 ferred to the genus Pterometra in 1918, since which time this genus has maintained 

 the same status. 



KEY TO THE SPECIES IN THE GENUS PTEROMETRA 



a 1 . No ventral spines on the longer proximal cirrus segments; no trace of carination on the division 



series; cirri numerous, XXX-XXXV; 20 arms. 



h 1 . Cirri excessively long and stout, from one-fourth to one-third again as long as the arms; all 

 10 columns of cirrus sockets closely crowded against each other (Philippine Islands; 77 



meters) magnipeda (p. 426) 



6 1 . Cirri shorter and more slender, usually from three-fourths to four-fifths of the arm length, 

 rarely as long as or somewhat longer than the arms; columns of cirrus sockets separated by 

 a narrow groove mterradially and by a broader space in the midradial line (Kei and Damar 

 Islands and eastern Java northward to the Gulf of Martaban and the southern Philippines; 



36 [730] 100 meters) pulcherrima (p. 427) 



o*. Longer proximal cirrus segments bearing on the midvential portion of the distal edge a long sharp 



