1884.] SPECIES OF OREASTER. 83 



to which one may suppose that the spines vary in length and 

 strength. 



The first explanation that one would be led to give would pro- 

 bably be to some such effect as this. Tlie specimen now under con- 

 sideration is larger than Dr. Liitken's specimens because it is better 

 provided with spines, and has therefore had less difficulty in main- 

 taining its existence. 



On the other hand, we do not and never can know what Dr. 

 Liitken's specimens might have accomplished in the way of growth 

 had they not fallen victims to the zeal of a collector. 



All, then, that we can say is, that of known specimens of Oreaster 

 gracilis the largest has the spines best developed. 



This statement does not, of course, exclude the possibility of 

 smaller specimens being also well provided with spines : if it did it 

 could never be allowed to pass by one who had gone over the col- 

 lection in the British Museum. Inasmuch as it tacitly allows that 

 small specimens may be well provided with spines on the dorsal 

 aspect of the disk, it raises the next question as to whether that 

 difference is one of race, of sex, or of an indefinite variability, not 

 yet seized upon to the profit of the species. In other words, it 

 raises questions which are beyond the ken of the cabinet naturalist, 

 but not questions which cannot be satisfactorily investigated by 

 those who are fortunate enough, as are some of our Australian 

 fellow-subjects, to have these creatures living in their own seas. 



One will perhaps be pardoned the apparent truism if attention is 

 directed to the fact that while a systematist measures spines by 

 millimetres, a Starfish may have them scattered in great abundance 

 over his whole body — in other words, accurate measurements must 

 always be used in an intelligent fashion, note being made of the 

 fact that a difference in length which, when measured by the ruler, 

 may amount only to h a millimetre, comes to be a matter of import- 

 ance to a creature which numbers these spines by hundreds. 



In the investigation of the spinulation of Starfishes there is, 

 surely, a wide field for the study of those mechanical causes with 

 which the zoologist is concerned. 



Oreaster grayi, sp. nov. 



Pentaceros nodosa, Gray, Ann. N. H. vi. p. 277 (1841). 



As we use Linnaeus's name nodosus for the species which he no 

 doubt so first named, we have to find another name for Gray's species. 



The following description is based on a specimen considerably 

 larger than Gray's " tvpe," which was obtained from Billiton : — 



R = 22r. Disk not high; arms very broad, even at the distal 

 end ; lophial ossicles with large tubercles in the place of more or 

 less sharp spines ; the apical spines not disproportionately large. A 

 few spines within the apical region. 



The superomarginal plates alone form the sides of the arm, they 

 are about 1 7 in number ; the inferomarginals are more numerous 

 by one or two ; of the former, some of the more distal are provided 



6* 



