Report on the zoological collections made in the Indo-Pacific Ocean ...

—164 COLLECTIONS FEOM MELANESIA.washed with purple ; the middle line of the arms is lighter, butpatches or spots of purple are to be found at the sides ; the lowersurface is a little lighter on the disk than on the arms, where it isalmost black.Port Mollo, 12 fms.Three smaller specimens alreadj^ in the collection of the BritishMuseum, from ]Sicol Bay, N.W. Australia, must, I think, bereferred to this species. The smallest of these has not more than30 cirri, nor have they more than 40 joints ; their spines, and especiallythe penultimate one, are better developed. There are onlyabout 50 arms, and in some cases there are only two palmars (whenthe axillary is not a syzygy). The ground-colour is purplish, markedwith yellow bands.16. Actinometra Solaris.P. H. Carpenter, Notes Leyd. Mtts. iii. p. 192 ; Journ. Linn. Soc, Zool.xvi. p. 514.Two specimens of different sizes do, I think, undoubtedly belong tothis species, to which specimens have not unfrequently been assignedthat are to be distinguished by what are apparently good specificcharacters.Prince of Wales Channel.The greatest difficulties attend the exact delimitation of the specificcharacters of this species ; and the question whether they vary withinwide limits or are, rather, sharply defined cannot yet be answered.For the purposes of exact knowledge it seems to be at present thebetter course to try and recognize points of difference betweenallied forms ; we must by experiment and experience discover whichof the characters of a Comatulid afford trustworthy criteria in thediscrimination of species ; so few forms have, as yet, been described,and so little criticism has been brought to bear on what work hasbeen done, that our knowledge of how species are to be defined anddelimited is as yet in a very elementary condition.The only consolation is to be found in the reflection that whatmay seem, with wider knowledge, to be a " bad species " is justifiablyregarded now as a " good one," and that wary specific discriminationis often a considerable aid to the exact and accurate knowledgeof the characters of complex and elaborate forms.The two specimens here ascribed to A. Solaris present the followingcharacters :There are 12 cirri, and there may be only 18 joints in acirrus ; the more proximal joints of the arms of the smaller specimenare more " knobby " than the correspondingly placed jointsin the larger. In both cases the arms are at their widest a Littledistance from the disk ; the keels on the basal joints of the secondpinnule are well marked in the smaller specimen ; but in neithercase are there any very prominent keels on the basal joints of thethird pinnules.