66 PROF. F. J. BELT, ON THE [Feb. 19, 



Oreaster nodxjlosus. 



Pentaceros nodulosus, Perrier, Rev. Stell. p. 237. 



R = 23 r. Disk moderately elevated, arms of moderate width, 

 tapei-ing gradually. The lophial and apical spiaes absent, and their 

 place taken by the enlargement of the ossicles into convex rounded 

 bodies. 



About 1 7 marginal plates in either series ; it is only in the more 

 distal regions that the inferomarginals take any share in forming the 

 sides of the arms. Neither series are spinose. 



Adambulacra] spinulation diplacanthid, the spines blunt ; in the 

 inner row there are ordinarily seven spines, of which the median are 

 the more prominent ; in the outer row there are two or three larger 

 spines, one of which is often, when only two are developed, much 

 larger than the other ; these spines have a direction a little oblique 

 to the longitudinal axis of the arm. Between the outer and inner 

 rows a well-developed forcipiform pedicellaria is placed. Beyond 

 the outer row there are irregularly shaped separate granules, which 

 appear, at first, to afford indications of a third row of adambulacral 

 spines. 



The ventral ossicles are often distinguishable from one another 

 owing to the larger size of the granules in the centre than at the 

 edge of the ossicle ; sessile valvular pedicellarise are richly developed 

 among the granules. Large and coarse granules are also to be 

 observed on the marginal plates, on which, however, pedicellarite are 

 only rarely developed. 



The upper surface, both of the disk and of the arms, is delicately 

 reticulated. The pore-areas are well separated from one another, and 

 are, in all the more proximal parts of the arm, of some size, and 

 contain more than twenty pores. 



The areas of the two lower series along the sides of the arms 

 sometimes become fused at certain points ; the lower series extend 

 into the space between every pair of superomarginal plates. The 

 granulation on the nodal points is rather more delicate than on the 

 ventral surface, and the sessile pedicellarise are exceedingly small. 



Nearly all the ossicles along the lophial line are enlarged ; some 

 are more so than the rest, and two or three generally attain to con- 

 siderable prominence ; those which flank the apical region are 

 large and rounded, and are, like the rest, covered with a close-set 

 investment of rather large flat granules. A few pedicellarise are to 

 be observed among the granules of the apical region, where no spine 

 or protuberance of any kind is developed. The madreporite forms 

 an elongated oval whose longer axis is directed downwards, and is 

 placed just outside the boundary of the apical region. 



Colour (dry) dirty yellow, probably deep yellow in life. 



Measurements : — 



R=53 ; r=2r5 ; breadth of arm at base 18. 

 R=70 ; ?-=30; breadth of arm at base 29. 



Hab. West Australia (Dick Hartog's Island). 



