PHOTOTYPE PLATE NO. XXVIII. 43 



structure, on near examination, is found to be a pedunculated, bladder-like membrane connected 

 with the vent, and communicating by a circular aperture with the exterior. On raising the 

 Sea-urchin above the surface of the water, the structure is immediately withdrawn into the cavity 

 of the body. It not improbably fulfils a respiratory function. Other structural points attract 

 notice in the living organism. Disposed at equal distances around the aboral aperture, with 

 its bulbous appendage, are five ovate pigment masses of a brilliant ultramarine-blue. These 

 structures, in accordance with the results of the most recent research, would appear to 

 possess all the essential elements of complex visual organs. In an allied, shorter-spined form, 

 Astropyga Firiidciihcrgi, obtained off the coast of Ceylon, recently described and illustrated in a 

 magnificent monograph by the cousins Dr. P. and Dr. F. Sarasin, similar brilliant blue visual 

 spots are developed in radiating lines throughout the surface of the shell or test, rendering 

 the organism exceptionallj' beautiful Outside the blue eye-spots in Diadema, five somewhat 

 large, irregularly ovate, pure white patches are usually visible. These are the discharged 

 products of the reproductive organs, and are commonl}' composed of a tenacious, exuding mass 

 of ova. 



The living corals conspicuous in this reef-view are few and far between. l"hey embrace for 

 the most part Brain-corals, Coeloriae and Goniastraeae. Dead coralla, more or less encrusted with 

 Alcyonarian polyparies, occupy the most extensive area; and many of these, where the Alcj'onaria 

 are absent, give support to colonies of the Frilled Clam, Tridaciia compressa, previously referred 

 to as a characteristic denizen of the Palm Islands reefs. 



A species of starfish that is abundant in the Palm Islands reefs, and also throughout the 

 Great Barrier district, is represented by Plate XL, Fig. 8, of the chromo-lithographic series. Its 

 technical name is Linckia Icvvigata but it differs conspicuously from its European congeners in 

 its unusual and exceedingly attractive colours. The entire body is dappled over with graduating 

 shades of the purest Antwerp blue, while the long tubular locomotor suckers or pedicels are 

 bright chrome-yellow. Two other members of the same echinodermatous, or sea-urchin and 

 starfish, class, observed on the Palm Islands reefs, are depicted in the same coloured plate. These 

 are the two Feather-starfish, Antcdon sp., represented by Figs. 7 and 7A, clinging to the corallum 

 of the Gorgonia in the right-hand upper corner. In general form they resemble the English 

 Feather-star, Coniatula rosacea ; but they possess about forty, in place of the ten, pinnate arms of 

 the European type. The variety of hues exhibited by this Barrier Reef species are legion, run- 

 ning through every gradation of tint from pale yellow to rose-pink, deep crimson and black, 

 and including every conceivable intermixture of those colours. One especially handsome racial 

 variety of this Feather-star, obtained at Thursday Island, had its fern-like arms resplendent 

 with shades of old-gold and bronze-green. The special biological interest attached to this 

 Feather-star group of starfishes is that they begin life attached to submarine objects by a 

 slender stalk. They_ subsequently become detached, and thenceforward lead a free-roving 



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