200 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



5538. Between Negros and Siquijor, 256 fathoms, green mud, sand, 

 bottom temperature 53.3° F. ; 3 specimens (large). 



CHEIRASTER DIOMEDEAE Fisher. 



Plate 47, fig. 1 ; plate 54, figs. 5, 5a-c. 

 CJwiraster diomedeae Fishee, 1917&, p. 90, 



Diagnosis. — Eays 5, long, slender, with narrow marginals carrying 



1 superomarginal and usually 2 inferomarginal spines; abactinal 

 plates, with 10 to 15 spinelets on disk, and on ray usually 2 to 7; 

 enlarged central spinules scattered on outer half or two-thirds of 

 ray ; adambulacral furrow spines 10 to 12 ; 1 subambulacral except on 

 outer part of ray, where there are 2 ; 11 to 13 oral, and 1 prominent 

 suboral spine. Papularia small, with about 25 pores, which do not 

 reach farther than opposite middle of third superomarginal. Pecti- 

 nate pedicellariae on the abactinal surface, between the proximal 

 superomarginals, over the intermarginal suture, on the actinal inter- 

 mediate plates; fasciculate pedicellariae on the actinal surface of 

 inferomarginals. Related to Ch. snyderi. R=86 mm., r=10 mm., 

 R=8.6 r; breadth of ray at base (between first and second supero- 

 marginals, 10 mm. ; at middle of ray, 5 mm. 



Description. — The groups of spinelets of the abactinal plates are 

 slightly spaced — usually about one-third the diameter of the pseudo- 

 paxilla, which consists, on the disk of 10 to 15 tapering rough spine- 

 lets, the 3 to 5 central variable in length, but ordinarily longer than 

 the peripheral. Some of them have a short central spinule overtop- 

 ping the rest, but not long enough to rank as an enlarged central 

 spine, the latter occurring on the outer half or two-thirds of the 

 ray, where the distinctly spaced pseudopaxillae have 2 to 7 short 

 delicate spinelets. Only a relatively few along the radial area have 

 an enlarged central spine. This is slender, rough, pointed, and 

 variable as to length, being proximally 3 to 5 times the length of the 

 ])eripheral spinelets, and distally upward to 10 times. Some of the 

 larger spines have 9 or 10 peripheral spinelets. Pectinate pedicel- 

 lariae are scattered on the disk and base of rays. They consist of 



2 combs of 3 to 5 pointed spines, 2 to 4 times longer than the ordinary 

 spinelets of the same plate. The 2 combs are on adjoining plates, and 

 appear to be a little less specialized than in Ch. gazellae^ inasmuch 

 as the plate is scarcely different from the other except for the pres- 

 ence of the slightly curved comb of sharp spines. Some combs do not 

 have a vis-a-vis. 



The papularia are small, with about 25 pores in 4 rows, the distal 

 end being scared}' two-parted. The papularium extends to opposite 

 tlie end of the second or the middle of the third superomarginal 

 plate, its total length being 6 to 7 mm. and breadth 4 mm., or, re- 

 spectively, O.G to 0.7, and 0.4, the minor radius. The small papu- 



