MONOGRAPH OF THE EXISTING CRINOIDS. 



289 



strong lateral compression of the cirri; in other words, the reduction of the calca- 

 reous base usually takes place faster along the transverse than along the dorso- 

 ventral axis. This condition is not found outside of the Macrophreata, where it is 

 especially characteristic of the Atelecrinid&a (figs. 405, 406, p. 311, and 414, p. 319), 

 the Pentametrocrinidse (fig. 404, p. 311), and the genera Psathyrometra (fig. 379, 

 p. 301), Thysanometra (fig. 372, p. 299), and Coccometra (figs. 374-376, p. 299) of the 

 Antedonidae. 



An increase in the stoutness of the cirri unaccompanied by any increase in the 

 length or in the number of segments indeed sometimes correlated with a reihic- 



FIG. 345. 



FIG. 346. 



^^^^ 



FIG. 347. 



FIG. 348. 



FlGS. 345-348. 345, A CIRRUS FROM A SPECIMEN OF CENOMETRA UNICORNIS FROM THE PHILIPPINE ISLANDS VIEWED (a) DOR- 

 SALLY AND (6) LATERALLY. 346, A CIRRUS FROM A SPECIMEN OF CYLLOMETRA ALBOPURPUREA FROM SOUTHERN JAPAN VIEWED 

 (0) DORSALLY AND (6) LATERALLY. 347, LATERAL VIEW OF THE CIKRUS OF A SPECIMEN OF CYI.LGMETRA MANCA FROM 



THE Kj ISLANDS. 348, A CIRRUS FROM A SPECIMEN OF CYLLOMETKA MANCA FROM THE Ki ISLANDS VIEWED (a) DORSALLY 



AND (&) LATERALLY. 



tion hi regard to the latter may be considered as among the chief characteristics 

 of the cirri of the Oligophreata, though it is much more marked in certain groups 

 or species than in others. In its simplest form it is best seen hi the Charitometridae 

 (figs. 99, p. 160, 100, p. 162, and 369, 370, p. 299) and Comactiniinae (figs. 76, p. 129, 

 and 327, 328, p. 281), and particularly in the Tropiometridse (figs. 88, p. 145, and 356, 

 p. 293), where it is not obscured by an increase in the length of the cirri. In 

 these forms the cirri, like those of most of the Macrophreata, are of the same 

 nature throughout and show no division into specialized areas. 



