A MONOGRAPH OF THE EXISTING CRINOIDS 159 



segments subequal in length, the distal with only slight paired tubercles on the dorsal 

 side. I remarked further than in C. manca the proximal cirrus segments are much 

 elongated, the distal short, with long bidentate or tridentato dorsal spines. The 

 number of arms in C.albopurpurea varies from 10 to 30, but is most commonly about 20. 

 The form referred to in these remarks is not manca but disciformis, as is evident 

 from the mention of the elongated earlier cirrus segments and the long dorsal spines. 

 In my key to the species of the genus Cyllometra published in 1918 I gave albo- 

 purpurea as having the cirrus segments subequal, mostly about as long as broad, the 

 outer with minute dorsal tubercles, whereas in manca, the outer cirrus segments are 

 broader than long and bear small, though prominent, dorsal spines. In view of the 

 great variability seen in specimens from Japan there can be little doubt that these 

 supposed differences are illusory, and that in reality albopurpurea is a synonym of 

 manca. 



Cyllometra anomala, which I described in 1908, is merely an aberrant individual 

 from southern Japan. 



On June 25, 1909, I described Cyllometra soluta from specimens from the Straits 

 of Ormuz at the entrance to the Persian Gulf. In the original description the only 

 tangible difference between soluta and previously described forms is that in soluta 

 P 2 is much more slender, and is nearly smooth. In the key to the species of Cyllometra 

 published in 1918 manca is said to have 19-29 arms, IIIBr series, and the outer edges 

 of the segments of P 2 with prominent spines at the prismatic angles, whereas soluta 

 has 14-18 arms, no IIIBr series, and the outer edges of the segments of P 2 with small 

 spines at the prismatic angles. These supposed differences are of little, if any, 

 significance, and undoubtedly soluta should be suppressed as a synonym of manca. 

 Dr. Torsten Gisl6n in 1922 described Cyllometra pulchella from the vicinity of the 

 Goto Islands, southwestern Japan. I can find nothing hi his description to indicate 

 any tangible difference between this supposed new species and manca as represented in 

 the same region. 



The forms described as Antedon manca, A. disciformis, Cyllometra albopurpurea, 

 C. anomala, C. soluta, and C. pulchella seem to me undoubtedly to represent the same 

 specific type. It is possible, however, that in the future some of these names may be 

 found useful for designating more or less marked varietal forms or geographical races. 

 Dr. Torsten Gisten made a very careful study of the various forms assigned to the 

 genus Cyllometra on the basis of a large number of specimens from southern Japan and 

 the Bonin Islands collected by Dr. Sixten Bock and Dr. Theodor Mortensen. 



In his report upon the crinoids collected by Dr. Bock he said that although 

 Cyllometra discijormis is evidently very closely related to C. manca he nevertheless 

 maintained them as separate species. He recalled that the author [in the Siboga 

 report published in 1918] differentiated disciformis from manca on the basis of its 

 elongated proximal cirrus segments, though stating at the same time that in disciformis 

 the length of the cirrus segments rapidly decreases with increasing depth of water. 

 He said that the deepest localities from which disciformis had previously been 

 dredged are at 180 fathoms (329 meters). The specimens he recorded and described 

 (from Bock's stations 12, ?33, and 35) were found at depths of 400 fathoms (731 meters) 

 and 90 fathoms (164 meters) to 200 fathoms (366 meters), and these have very short 

 cirrus segments approaching those of manca. 



