MADREPORx\RIAN CORALS 71 



weighs a little over 2 lb., and no doubt larger specimens 

 than this have been found. 



The development of Herpetolitha has not yet been fully 

 worked out, but the presence of a distinct scar on the under 

 side of small specimens leaves no doubt that in the early 

 stages it is provided with a stalk of attachment as in Fungia. 



PoLYPHYLLiA. — The final stage in this series of genera 

 is found in Polyphyllia, in which the sharp distinction 

 between calices of the median groove and the lateral calices 

 tends to become lost, and the corallum seems to be composed 



Fig. 26. — Siderastraea radians. West Indius. A small specimen. Xat. size. 



of a number of very irregular and incomplete calices of 

 various sizes. 



All these genera, except Fungia, are confined to shallow 

 water of the tropical Indo-Pacific regions. 



The genera of the family which have been described 

 above are all free in the adult stage, those that are still 

 to be considered are permanently attached to some other 

 coral or rock. 



SiDERASTRAEA. — The gcuus Siderastraca (Fig. 26) in- 

 cludes a number of corals which are very abundant on the 

 West Indian reefs and occur also in the Indian Ocean and 



