A MONOGRAPH OF THE EXISTING CRINOIDS 73 



Monachometra cf.fragilis GISLN, Zool. Bidrag Uppsala, vol. 9, 1924, pp. 44, 51; fig. 14, p. 48 (base of 

 a postradial series). 



Perissomelra cf. aranea GISLN, Zool. Bidrag Uppsala, vol. 9, 1924, p. 80 (note on syzygial faces). 



Perissometra carinata GisLfin, Vid. Medd. Dansk Naturh. Foren. K0benhavn, vol. 83, 1927, p. 2 

 (station 9; 162 meters), p. 34 (station 9; description; comparisons), p. 68 (listed), figs. 24, 25, p. 37, 

 pi. 2, fig. 84; Vid. Medd. Dansk Naturh. Foren. K0benhavn, vol. 93, 1933, p. 481. 



Monachometra mortenseni GISLN, Vid. Medd. Dansk Naturh. Foren. K0benhavn, vol. 83, 1927, p. 2 

 (station 9; 162 meters), p. 35 (station 9; description; comparisons), p. 68 (listed), figs. 26, 27, p. 37, 

 pi. 1, fig. 83; Vid. Medd. Dansk Naturh. Foren. K0benhavn, vol. 93, 1933, p. 481. 



Monachomelra fragilis Gisi.fiN, Vid. Medd. Dansk Nalurh. Foren. K0benhavn, vol. 83, 1927, p. 38 

 (comparisons); Kungl. Fysiograf. Sallsk. Handl., new ser., vol. 45, No. 11, 1934, pp. 18, 21. 



Diagnostic features. The arms beyond the proximal more or less oblong brachials 

 are distinctly carinate; the cirri arc short, about one-fifth of the arm length, with usually 

 20-25 segments of which the eighth is a transition segment and the distal are broader 

 than long with strong carinate processes or blunt dorsal spines; and the lateral portions 

 of the division series and first two brachials may be unmodified or more or less exten- 

 sively irregularly tubercular, with or without a fine median raised line. The 10-18 arms 

 are 125-140 mm. long, and the cirri are 20-25 mm. long. 



Description of the type specimen. The centrodorsal is a thick disk with the flat 

 and somewhat roughened dorsal pole broad, 4 mm. in diameter and the sides practically 

 vertical. The cirrus sockets arc arranged in 15 closely crowded columns of one or two 

 each. 



The cirri are XXI, 15-25, from 20 to 25 mm. long, almost or quite straight in the 

 proximal third and strongly and regularly recurved in the distal two-thirds so that the 

 extreme tip is parallel with the basal portion. In a fully developed cirrus the first 

 segment is very short, in some cases only the dorsal half projecting beyond the cirrus 

 socket; the second is about three times as broad as long, the proximal border with a 

 strong broadly rounded median angle and the distal border concave; the third is about 

 twice as long as the greatest (midlateral) length with the proximal and distal borders 

 as in the preceding though with the curvature somewhat less pronounced; the fourth is 

 half again as broad as long; the fifth is about as long as, or slightly longer than, broad; 

 the sixth is slightly longer; the seventh is about one-third again as long as broad; and 

 the eighth, a transition segment, is twice as long as the median width. The transition 

 segment, usualty the eighth though often the seventh, is basally slightly less in width 

 than the distal end of the segment preceding; it tapers markedly in the proximal two- 

 thirds, in the distal third increasing slightly in width; the proximal two-thirds has a 

 dull surface like that of the segments preceding but is darker in color; the distal third 

 is very light with a polished surface like the following segments. The cirri arc stout 

 at the base but taper rather abruptly on the transition segment so that the portion 

 beyond that segment is in lateral view only about three-quarters the width of the basal 

 portion. The segments immediately following the transition segment are more or less 

 longer than broad, but after one or two they become slightly broader than long. These 

 segments have a median dorsal carination which at first is rounded but soon becomes 

 sharp. In lateral view the profile of the dorsal surface of these segments rises in a 

 curved convexity from the proximal to the distal end so that the distal end projects 

 beyond the base of the segment next following and may sometimes be produced into a 

 short sharp point. The opposing spine is represented by a low subterminal elevation 



