58 BULLETIN lOO, UNITED STATES NATIONAL MUSEUM. 



Adambulacral plates strongly angular, the adoral facet the shorter. 

 Furrow spines 12 or 13, terete, capitate, in a palmate series and 

 basally webbed. The spines near apex of angle are the longest (about 

 equal to length of plate) thence decreasing in length toward either 

 end of series. A pointed, specialized subambulacral spine, situated 

 on the outer aboral corner of plate, is present, accompanied some- 

 times by a shorter companion, while 3 or 4 other shorter spines 

 occur on the margin of plate, all immersed in membrane. The 

 first dozen plates have the marginal spines subequal, or one slightly 

 enlarged, and all more or less completely involved in membrane. 

 Here and there a plate is partly separated from the actinals by a 

 groove ; usually the skin is continuous between actinals and adambu- 

 lacrals. First adambulacral not markedly compressed. 



Mouth plates large, the combined pair truncate at inner end. Mar- 

 ginal series of spinelets, 13, strongly angular, the spinelet at apex 

 being deep in furrow, and the rest unequal ; inner one or two enlarged 

 into teeth. About half the spinelets face on actinostome and the 

 rest on the furrow. Furrow surface of plate excavated for first 

 tube foot. Surface of plate with 20 to 30 spinelets, about 10 of which 

 border median suture and the rest stand below these in a couple of 

 very irregular and variable series. 



Madreporic body -very large, in diameter equal to the length of 

 the first 3 superomarginals, and situated twice its diameter from 

 margin. Striae fine, radiating from a point midway between center 

 and adcentral (inner) margin. 



Type.— Cfxt. No. 30509, U.S.N.M. 



Type-locality. — Station 5624, between Gillolo and Makyan Islands, 

 Molucca Islands (lat. 0° 12' 15" N.; long, 127° 20' 30'' E.), 288 

 fathoms, fine sand, mud. 



Distribution. — Molucca Islands, 230 to 288 fathoms. 



Specimens examined. — In addition to the type, an abnormal ex- 

 ample from station 5625, between Gillolo and Kayoa Islands, Mo- 

 lucca Islands (lat. 0° 07' K; long. 127° 28' E.), 230 fathoms, gray 

 mud, fine sand. 



Remarks. — The following differences separate this species from the 

 two preceding: The paxillae are much larger, with many more spine- 

 lets; the superomarginal spinule is inconspicuous and present only 

 on the middle portion of ray. Megaloplax is :3eparated from analo- 

 gus by several additional characters: The large madreporic body; 

 superomarginals not touching along the radial line, distally; more 

 open cribriform organs; first adambulacral not markedly com- 

 pressed ; odd interradial double series of actinal intermediate plates 

 conspicuously broader at inner end (more than 3 times width of 

 outer end) ; furrow spinelets 12 to 13 (10 or 11 in aruilogus). The 



