A MONOGRAPH OF THE EXISTING CRINOIDS 271 



GLYPTOMETRA LEVIGATA (A. H. Clark 



Plate 27, Figures 82, 83 

 [See also vol. 1, pt. 2, fig, 671, p. 335.] 



Pachylometra levigata A. H. Clark, Proc. U. S. Nat. Mus., vol. 36, 1909, p, 406 (description; Albatross 

 station 5236) ; Crinoirls of the Indian Ocean, 1912, p. 224 (synonymy; locality); Unstalked crinoids 

 of the Si&oja-Exped., 1918, p. 184 (in key; range), p. 1S5 (references). 



Pachylometra laevigata Gislem, Vid. Medd. Dansk Nat. Foren. K0benhavn, vol. 93, 1933, p. 482 

 (perhaps a species of Crinomctra) . 



Diagnostic features. — The cirrus sockets are arranged in 15 columns on the centro- 

 dorsal ; the cirri are 15 mm. long with 14-15 segments, all of which are longer than broad, 

 the longest earlier segments half again as long as broad; the 12-14 arms are 100 mm. 

 long; and the division series and arm bases are smooth, without ornamentation. 



Description. — The centrodorsal is thick-discoidal or more or less columnar with the 

 flat polar area 2.5 or 3 mm. in diameter. The cirrus sockets are arranged in three col- 

 umns in each radial area, the two outer columns converging distally and usually meeting 

 beyond the middle column. The columns are usually separated by more or less de- 

 veloped ridges. 



The cirri are XXX-XXXV, 14-15, 15 mm. long. The first two segments are 

 about twice as broad as long, the third is about as long as broad, and the fourth to the 

 seventh or eighth are half again as long as broad; the segments following gradually 

 decrease in length, the third and fourth from the end being only slightly longer than 

 broad. The terminal segments are again about half again as long as broad. The distal 

 ventral ends of the segments are slightly prominent, and the distal dorsal ends of the 

 outer segments are sometimes slightly thickened. The opposing spine is minute, 

 terminally situated, and directed obliquely forward; it is often barely indicated or 

 entirely absent. The terminal claw is nearly as long as the penultimate segment, 

 moderately slender and moderately curved. 



The ends of the basal rays are usually visible as dorsoventrally elongate tubercles 

 in the angles of the calyx, but are sometimes quite concealed. 



The radials are concealed. The IBr, are usually entirely concealed in the median 

 line but slightly visible over the ends of the basal rays; they are sometimes visible as a 

 narrow line along the proximal border of the axillaries. The IBr 2 (axillaries) are rhom- 

 bic, twice as broad as long, with all the sides somewhat incurved, and rise in the proximal 

 half to a large rounded tubercle. The IIBr series are 4(3+4), rarely 2, in close apposi- 

 tion and strongly flattened laterally. 



The 12-14 arms are 100 mm. long. The first eight or nine brachials arc wedge- 

 shaped or almost oblong, about twice as broad as long, and are more or less tubercular. 

 The brachials following arc triangular, about as long as broad, becoming in the ter- 

 minal portion of the arms wedge-shaped and longer than broad. 



In arms arising from a IBr axillary the first syzygy is between brachials 3+4, the 

 second between brachials 14 + 15 or 15 + 16, and the distal intersyzygial interval is 

 from 6 to 16 oblique muscular articulations. In arms arising from a IIBr axillary the 

 first syzygy is between brachials 1+2 or 2 + 3. 



The pinnules resemble those of G. angusticalyx, but the expansion of the genital 

 pinnules is somewhat more marked. 



