MONOGRAPH OF THE EXISTING CRINOIDS. 



277 



reduced merely to a small conical terminal button with little or no trace of the 

 hard vitreous cortical layer typically present (figs. 372, 376, p. 299, and 404, 406, 

 p. 311) ; similarly, in species with very long and spiny cirri, such as those belonging 

 to the genera Asterometra, Ptilometra, Pteromelra, Zencrmetra, Thalassometra, Cosmio- 

 metra, etc., which live attached to rocks or to calcified or chitinous organisms where 

 no penetration by the terminal claw is possible, that organ has become, together 

 with the penultimate segment, quite insignificant, no longer performing any special 



f 



FIG. 321. 



FIG. 322. 



2II 



FIG. 323. 

 FIGS. 321-323. 321, A CIRRUS FROM A SPECIMEN OF COMATELLA NIGRA FROM THE I'HILIPPINE ISLANDS VIEWED (a) DOKSALLT 



AND (6) LATERALLY. 322, LATERAL MEW OF A CIRRUS FROM A SPECIMEN OF ("APILLASTER MARLE FROM SOUTHWESTERN JAPAN, 

 323, A CIRRUS FROM A SPECIMEN OF CAPIIiASTER MULTIHADIATA FROM THE 1'IIILIPriNE ISLANDS VIEWED (a) DOHSALLY AND 

 ((>) LATERALLY. 



function of its own, but serving merely to assist the dorsal spines in roughening 

 the dorsal surface of the cirri, the gripping action being effected entirely by the 

 embracing of the object of attachment without penetration (figs. 94, p. 155, and 363, 

 364, 366-368, p. 297). 



The terminal claw possesses a very dense cortical layer, vitreous in appearance, 

 which envelops a core of lesser density, resembling the entire substance of the pre- 

 ceding segments. This cortical layer at the base is very tliin, but it gradually 



