MONOGKAPH OF THE EXISTING CRINOIDS. 



141 



are found in Leptometra (fig. 370, p. 237), though here two pinnule pairs are 

 involved instead of only one. 



In the Pentametrocrinida (fig. 286, p. 215, and part 1, fig. 113, p. 181; 119, 

 p. 185; 120, p. 187; and 121, p. 189), Thysanometrinte (figs. 282, p. 215, and 378, 

 p. 243). and Heliometrinse (figs. 292-294, p. 221) all the pinnules are much elon- 

 gated, and the oral pinnules, including the first pair only in the Pentametro- 

 crinidae and Thysanometrinse, but the first two to six pairs in the Heliometrinse, 



Fio. 205. LATERAL VIEW OF YOUNO SPECIMEN OF PTILOMETBA MACBONEMA FROM SOUTHWESTERN ADSTEALIA. 



are but little, when at all, longer than those following. They are composed of 

 very short segments, with the corners so cut away that they appear hexagonal 

 in lateral view, and are exceedingly flexible, contrasting strongly in this respect 

 with the less mobile succeeding pinnules. 



In the species of the genera Perometra (fig. 319, p. 227), Erythrometra, 

 Toxometra, Eumetra, Iridometra (fig. 301, p. 221), Andrometra, and Dorometra 

 the pinnules of the first pair are tactile in character, though shorter than usual, 

 but the pinnules of the second and sometimes also of the third pair are much 

 enlarged and stiffened, in life projecting outward over the disk and forming a 



