266 BULLETIN 82, UNITED STATES NATIONAL MUSEUM 



ferred to the genus Crossometra; he rem^ked upon the unsatisfactory nature of Perisso- 

 metra and Crossometra as understood by me. In 1934 he discussed what he termed the 

 Pachylometra angusticalyx type of arm branching. 



GLYPTOMETRA SPAKKSI (John) 



Pachylometra, n. sp., A. H. CLARK, Proc. U. S. Nat. Mus., vol. 40, 1911, p. 51 (lat. 1420' N., long. 

 5230' E., 1,200 fathoms; Electro); Crinoids of the Indian Ocean, 1912, p. 224 (same) ; Smithsonian 

 Misc. Coll., vol. 61, No. 15, 1913, p. 70 (same); John Murray Exped. 1933-34, Sci. Rep., vol. 4, 

 No. 1, 1936 (Jan. 1, 1937), pp. 101 (same), 104, 105. 



Perissometra sparksi JOHN, Ann. Mag. Nat. Hist., ser. 10, vol. 20, p. 161, August 1937. 



Diagnostic features . The cirri, which are heavy and strongly curved, are arranged 

 in 10 columns on the centrodorsal ; they are composed of 14-21 segments of which all 

 but the basal are longer than broad; there are 14 arms in the type specimen; and the 

 division series and arm bases are moderately broad and smooth. 



Description. The centrodorsal is a thick disk with a flattened dorsal pole and 

 strongly produced interradial angles. The cirrus sockets are arranged in 10 columns of 

 3 each, 2 columns in each radial area. The two columns in one radial area touch at the 

 dorsal pole but diverge toward the periphery so as to run to the interradial angles. The 

 two adjacent columns of contiguous radial areas are in close contact. 



The cirri are XXXI, 14-21, heavy and strongly curved. The first three segments 

 are broader than long, the first more so than the second, and the second than the third. 

 The fourth is as long as broad. The remainder are longer than broad, the sixth to about 

 the tenth being more than half again as long as broad; those beyond decrease very 

 slightly in length. The articulations are only a little swollen. There is no trace of 

 dorsal spines. The distal half to third of the penultimate segment, the opposing spine, 

 and the terminal claw are sharply marked off through being of a lighter color than the 

 rest of the cirrus. The opposing spine is low, or very low. The terminal claw varies 

 from stout, moderately curved, and shorter than the penultimate segment to small and 

 less than half as long as the penultimate segment. 



The ends of the basal rays and the radials are concealed. The IBr t are short and 

 roughly crescentic. They are longest (1) in the midradial line where they are produced 

 backward between the interradial corners of the centrodorsal, either narrowly to a point, 

 or more broadly not to a point, but evenly; and (2) laterally where they are produced 

 anteriorly alongside the IBr 2 , which they therefore appear to grip. The proximal edge 

 is variable and uneven. The distal edge is produced into a rounded angle in the midline 

 incising the posterior angle of the IBr 2 . The IBr 2 (axillaries) are about three times as 

 broad as the greatest length, which is along the median line. The proximal and distal 

 edges of the middle two-thirds of the ossicle are convex, the former more strongly so 

 than the latter except that it is incised in the midline by the IBr t . Each lateral sixth 

 beyond the projections of the lateral edges of the IBrj is marked off by a constriction, 

 and each is square and incises the proximal exterior corner of the IIBri beyond it. The 

 distal median portion of the IBri is very slightly elevated to form a low wide inconspic- 

 uous mound with the proximal median portion of the IBr 2 , which is similarly raised. 

 The IIBrj has the shape of a thick shallow cup, the median two-thirds of the distal half 

 being deeply excavated. The proximal edge of the median two-thirds of the IIBr 2 is 

 produced backward to occupy the concavity in the IIBr^ its distal edge is faintly con- 

 cave. The ossicles of the division series are free from tubercles. Their dorsal surfaces 



