302 BULLETIN 82, UNITED STATES NATIONAL MUSEUM. 



like the paired spines in Cenometra, assumes a median position shortly after its appear- 

 ance; in the species of the genus Oligometrides (fig. 353, p. 293) the transverse ridge 

 moves to a position near the proximal edge of the segments, and a second transverse 

 ridge appears near the distal edge. The opposing spine of Oligometra (fig. 352, 

 p. 291) is slender, median, and perfectly erect, and the terminal claw, as usual in 

 the Oligophreata, is rather stout and strongly curved in its proximal third, becom- 

 ing more slender and nearly straight distally. The cirri in Cyllometra (figs. 346- 



348, p. 289) in general resemble those of Oligometra, but they may be even more 

 primitive in having some of the earlier segments slightly elongated, though this 

 is only the case in a few species; the transverse ridge may be very high, taking 

 the form of a high tri- or bidentate dorsal spine. The cirri of Decametra (fig. 



349, p. 291) and Petasometra are just like those of Cyllometra. The cirri of Colobo- 

 metra (fig. 350, p. 291), which are much elongated, are composed of segments which 

 are sometimes longer than broad proximally, very short distally; at first there 

 is a serrate transverse ridge, formed by the recession of the everted distal dorsal 

 ends of the segments, which soon divides in the middle and resolves itself into a 

 pair of dorsal spines; at the extreme tip these two spines fuse into one. The 

 proximal cirrals of Colobometra, like those of Zenometra (fig. 109, p. 175), have 

 the distal edges all around armed with long sharp spines, like the edges of the 

 calyx plates. 



The cirri of the species of Atelecrinidse (figs. 405, 406, p. 311, and 414, p. 319), 

 except Atelecrinus anomalus, are but imperfectly known, as the perfect tip has 

 never been observed. So far as can be seen they are of the same smooth, strongly 

 compressed type as that found in all of the Pcntametrocrinidse, and in such genera 

 as Iridometra, Coccometra, Psathyrometra and Thysanometra; except in Atelecrinus 

 anomalus (fig. 414, p. 319), which has cirri resembling those of Pentametrocrinus 

 tuberculatus , the component segments are greatly elongated, with somewhat swollen 

 distal ends, which are often more prominent along the ventral profile than along 

 the dorsal, the reverse of what is usually the case. At the present state of our 

 knowledge this feature is sufficient to identify the cirri of this family. 



In the Pentametrocrinidse (figs. 113, p. 181, 119, p. 185, 120, p. 187, 121, p. 189, 

 and 404, p. 311) the cirri are smooth, with more or less, often greatly, elongated 

 segments, which are strongly compressed laterally. In the species with very long 

 cirri, like Pentametrocrinus varians (fig. 119, p. 185) or P. japonicus (fig. 404, p. 311), 

 these end in a small, short and straight conical terminal claw; but in the species 

 with short cirri, like P. diomedese (fig. 120, p. 187) or P. tuberculatus (fig. 121, 

 p. 189), the terminal claw is considerably longer than the penultimate segment, 

 stout basally but tapering distally, comparatively straight in the basal half, but in 

 the distal half strongly curved downward. 



The cirri of the species belonging to the large family Antedonidse, as would 

 be expected, exhibit a very great degree of variation, though they are all constructed 

 after the same general plan. They may be described as more or less compressed 

 laterally, especially in the distal portion, slender, the earlier segments more or less 

 elongated and centrally constricted, the outer becoming slightly shorter, though 

 never very short, and without true dorsal spines (except in Zenometra), though the 



