202 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



and Ch. niasicus. One or 2 small spinelets stand on either trans- 

 verse margin of plate and 1 or 2 near the outer margin. 



Actinal intermediate plates 16 to 20 to each area and extending 

 to middle or end of second inferomarginal. Each area has 8 to 10 

 conspicuous pectinate pedicellariae, the largest with 5 or 6, some- 

 times 7, sharp spines, of the characteristic Cheiraster form, to each 

 curved comb. General surface of plates with short, equal, slender, 

 spaced spinelets as long as those of inferomarginals, and to each 

 area 1 to 3 plates have an enlarged spinule. 



Mouth plates with 11 to 13, usually 12, marginal spines, the inner 

 truncate or round tipped, broad, and about half as long as the inter- 

 radial suture between the 2 plates; the next is blunt, about half as 

 broad and three-fourths as long, while the remaining spines re- 

 semble those of the first adambulacral. There is 1 suboral spine to 

 each plate, near the free margin and a little nearer the aboral than 

 the inner corner. It is not quite so long as the first subambulacral. 

 There are 18 to 20 short, tapering, pointed spinelets on the convex 

 surface of the plates; 1 just back of the inner marginal spine is inter- 

 mediate in size between the spinelets and the suboral. 



Madreporic body large, with a large plate on its inner side and 7 

 other rather large plates (in addition to about 3 small) surrounding 

 it. Ridges irregular, transverse, in an interradial direction. It is 

 situated its own diameter from margin. 



Type.—C^t. No. 37035, U.S.N.M. 



Type-locality. — Station 5512, Iligan Bay, north coast of Minda- 

 nao, 423 fathoms, gray mud, fine sand, bottom temperature 52.8° 

 F. ; 1 specimen. 



Distribution. — Known only from the type-locality. 



Remarks. — This species may be distinguished from Ch. inops by 

 the absence of scattered, enlarged, central paxillar spines on the 

 disk and by the presence of abundant conspicuous pedicellariae; by 

 the more numerous furrow and oral spines and the absence of a sec- 

 ond subambulacral spine on the first adambulacral plate. It may be 

 distinguished from Ch. niasicus by its lack of enlarged abactinal 

 spines on the disk, by its very narrow superomarginals (in niasicus 

 they are wider than long), by the narrower inferomarginals, moi*e 

 numerous oral and subambulacral spines, and by the absence of a 

 second subambulacral spine on the first plate. The marginal plates 

 of nicsicus are rather heavy; in dio7nedeae they are relatively small. 

 Ch. snyderi seems to be the nearest relative. It has, however, fewer 

 adambulacral and oral spines, a second subambulacral spine on the 

 fii*st plate, broader inferomarginals with longer miliary spinelets, 

 shorter and stouter major marginal spines, and several conspicuous 

 accessory inferomarginal spinules. Further snyderi has shorter rays, 

 shorter abactinal spinelets, lacks the conspicuous inferomarginal fas- 



