DISTRIBUTION OF TYPES OF CALICLE. 143 



Bahamas 1 (PI. IV. figs. 2, 5, 6). The septa are short, irregular, and slightly 



knobbed. See also A. 

 West Indies x. 27 (PI. VI. figs. 6 and 7). The septa are irregular in length and 



thickness, with sharp or bent tips. 

 West Indits x. 28 (PI. VI. fig. 8). The septa are thick, wedge-shaped, with very 



sharp points; the thick skeletal elements are so perforated as to appear 



broken up at the surface. 



APPENDIX TO TABLE IV. 



One additional variation which has been mentioned once or twice in the descriptions 

 deserves notice. It is of special interest taken in conjunction with the fact that the calicles 

 of the Atlantic and West Indian Porites differ from the Indo-Pacific forms in the greater 

 thickness of their skeletal elements. Calicles appear with quite a delicate filigree skeleton at 

 the surface, but on close examination this surface pattern appears as if it were standing on a 

 flaky layer. The section shows, however, that these are not flakes but sudden thickenings of 

 the deeper elements. It is impossible to say for certain what is the meaning of this. It might 

 perhaps, on the one hand, indicate that the thickness of the elements characteristic of the 

 Porites of this region is secondary, and that the thinner skeleton of the Indo-Pacific Porites 

 was the original condition, and that we could see in these cases a transitional process from 

 the one condition to the other. But on the other hand of course the delicacy of the surface 

 elements in these individual cases might be secondary. 



The forms in which this sudden thickening just below the surface has been most noticed 

 are : — 



P. Florida 2. 



P. Florida 5. 



P. Bermnida 1. 



P. West Indies x. 14. 



P. West Indies x. 23. 



Note on the Blue Coloue of Individual Coralla. 



On p. 50 attention is called to the blue colour which appears sporadically in the Stony 

 Corals. It seems to differ from the ordinary colouring matters which are withdrawn with the 

 living layer, leaving the skeleton white. The blue colour very frequently persists, and further, 

 is not removed by any ordinary bleaching process. In this persistence and resistance to 

 bleaching it resembles the normal blue colouring matter of Heliopora coervlea* but whether 



* See Moseley, Phil. Trans, clxvi. part 1 (1876) p. 102. 



