148 ME. H. M. BEEIS'AED OIN" EECEISTT POEITID^. 



reason be removed from the family. Further, a review of 

 the structural variations not only within the genus, but even of lea 

 on one and the same specimen, reveals a correlation between the 

 wall and the pali, so that when the one is specially well developed 

 the other is correspondingly aborted. In Goniopora we have 

 the species G. Stohesi, in which the walls are high and the 

 pali are either absent or else only hinted at. And lastly, forms 

 occur, and will shortly be described, in the Indo-Pacific area 

 which show this same variation, viz., absence of pali. There 

 seems to me, then, no special advantage in separating a few 

 specimens of Porites because the deepening calicles have led to 

 the partial or complete suppression of the pali. This variation 

 seems to me not too great to be comprised within the range 

 embraced by the genus. 



In connection with what has been said above about the relation 

 of Porites to the Madreporidse, the resemblance between these 

 " Neoporites " of Duchassaing and Michelotti, in which the pali 

 are absent from the deep central calicles, and Montipora is very 

 interesting : it shows how along two different lines almost the 

 same structure may be reached. That these forms are not 

 Moutiporids may be gatliered — (I) from their habit, which is 

 more like that of Porites than of Montipora ; (2) from the walls 

 being more boldly reticular than in the majority of Montipores ; 

 (3) in the presence of a columella-tangle slowly filling up the 

 fossa, this being characteristic of the Poritidae but not of the 

 Madreporidse (excl. Turhinaria) ; (4) in the traces of pali ia the 

 shallower young calicles ; (5) ia the twelve septa nearly equal in 

 size, whereas in Montipora six, with a rudimentary second cycle, 

 is the usual septal formula. 



SUMMAET. 



The foregoing pages contain a preliminary instalment to a 

 revision of the classification of the Madreporaria by Milne- 

 Edwards and Haime, which has been rendered necessary by 

 recent advances in our knowledge of the morphology of the 

 coral-skeleton. 



The object of the paper is to record the results, obtained 

 during my work of cataloguing the specimens in the Natural 

 History Museum, as to the position of Porites among the 

 Madreporaria. A brief sketch of the history of the question 



