ME. H. M. BEENARD ON EECENT PORITID^:. 127 



Eecent Poritidce, and tbe Position of the Family in the Madre- 

 porarian System. By Henrx M. Bebnakd, M.A., F.L.S. 



[Eead 2nd February, 1899.] 



In the last paper dealing with the Stony Corals which I had the 

 honour of reading before this Society *, a phylogeny of the 

 Madreporarian skeleton was sketched out, and suggestions were 

 made as to the lines of development which had been taken by 

 some of the better-kcown recent forms. I now propose to give 

 an instalment of the morphological results of work done during 

 the past eighteen months on one of the families mentioned in 

 that paper — the Poritidae. It is hoped that in the course of the 

 next few years the remaining groups of the Madreporaria, both 

 recent and fossil, will be dealt with, and the proposed phylo- 

 genetic scheme completed and strengthened by additions and 

 amendments suggested in the course of the work. 



In this paper I propose to confine myself to the systematic 

 position of the Poritidse, and to introduce only so much structural 

 detail as is necessary. The variations of form assumed by Porites, 

 a few of which are only incidentally referred to here, deserve 

 separate description. The most important question raised by the 

 work itself, however, was primarily the place of the Poritidse 

 among the Madreporaria. This point has therefore been worked 

 out first, and the present paper will be shortly followed by a 

 more detailed account of the structure and of the chief lines of 

 differentiation found within the constituent genera. 



But, while reserving an account of the structure for fuller 

 treatment in a second paper, a brief description of the corals 

 known as Porites will doubtless add to the interest of the fol- 

 lowing pages. Although both explanate and branching forms 

 are known, the most familiar are smooth round masse-^, some- 

 times attaiuing a circumference of 60 feet. They are built up 

 by a dense crowd of minute cylindrical polyps characterized by 

 twelve short, thick, (?) rudimentary tentacles. The polyps rise 

 fairly high above their skeletal substratum, and when retracted 

 are unable to withdraw entirely into their calicles, as is the usual 

 habit in the Stony Corals. Examination of the dried skeleton 

 shows that the pits are too shallow to take in the polyps ; they 



* Journ. Linn. Soc, Zool. xxvi., read December 1897. 



