144 ME. H. M. BEEOS'AED ON EECEKT POEITID^. 



Id which the thickened walls show tendencies to form exli-a 

 ridges and hillocks closely resembling those of Montipora ; 

 indeed, but for the calicles, such specimens would certainly be 

 classed in that genus. These were not known when Quelch 

 made his new genus *. There are, however, a good many in the 

 British Museum collection. It seems to me as impossible to 

 separate them from Porites because of this rising of the wall, as 

 it is to separate 8ynar<sa on account of the sisking of the wall. 

 If ill e calicles are huilt on tlie same pZ«?z, variations in height 

 of the wall can hardly be considered as generic distinctions. 



Both these genera therefore, Spiarcea and Napopora, are 

 merged in the genus Porites. 



Mhodarcea. — This genus was established by Milne-Edwards and 

 Haime t, and was thought to differ from Goniopora in that the 

 latter had tall thin walls and spongy columella, while Bliodansa 

 had thick low walls with a rosette of pali rising off the columella. 

 These differences are only slight variations on the same essential 

 structure. Even in individual stocks, the development of the 

 pali is always the inverse of that of the walls ; where walls are 

 low, the pali are high and conspicuous. In any extended survey, 

 it is found absolutely impossible to separate the specimens on 

 these hues. I propose therefore to merge this genus into 

 Groniopora. 



Tichopora, Quelch %.■ — The union of Goniopora and RTiodarcea 

 forms a group which absorbs this proposed genus, in that it came 

 somewhere between them, differing but slightly from either. 



Alveopora. — This genus was the subject of my former paper 

 (Z. c), so that I need only repeat the conclusion at which I have 

 arrived, that, in spite of its occasional resemblance to individual 

 forms of Goniopora, as a primitive type of coral it is yet very 

 far removed from the Poritidse, which must rank among the mo&t 

 specialized of the Madreporaria. 



Coscinarcea, M.-E. & H. — Very little is known of this genus. 

 Only one species seems to be known. It was first figured in 

 Savigny's ' Descr. de I'Egypte,' pi. v. fig. 4, 1809, and named 

 Meandrina. These are very puzzling figures, and hardly suggest 



* Ann. & Mag. Nat. Hist. xiii. (1883) p. 296. 



t C. E. xxix. p. 259 (1849). 



i Chall. Eep. xvi. (1886) p. 188. 



