128 Mr. H. M. Bevnavd on the 



daughters appear from the sides of larger parent (" apical ") 

 poljps, was described as centrifugal, while that in Anacro- 

 jpora^ in which an apex of undifferentiated coenenchyma takes 

 the lead and the young polyps appear in it as it grows, was 

 called centripetal. The distinction was thought to be fanda- 

 mental. On the other hand, the new genus came very near 

 Mordipora, differing from it chiefly in the fact that the calicles 

 in Montipora are typically immersed, while in Anacropora 

 they bulge up the surfaces of the branches into mounds or 

 eminences. 



The new genus was accepted at once by Duncan in his 

 revision of Milne-Edwards and Haime's system, and he 

 allied it with Montipora. 



The ' Challenger ' expedition brought home two new types, 

 which Quelch classed under Ridley's genus, and in 1892 

 Rehberg * added another specimen and type, bringing the 

 number up to four. The following notes are based upon the 

 study of the specimens and fragments (twenty-two in all) in 

 the National Collection. These include all the existing types 

 except that of Rehberg {A. spinosa),vi\\\c\\ is in the Ham- 

 burg Museum. The examination has resulted in the 

 establishment of two new types, one being represented only 

 by fragments, the bulk of the specimens being in the Vienna 

 Museum. Full details will appear in the official catalogue, 

 which is in the press. 



I was for some time quite uncertain as to the validity of 

 the distinction made by Ridley between Anacropora and 

 Montipora. Slight mounds or elevations on which the calicles 

 opened might and do, indeed, occur in Montipora, wherever 

 the corallum is very thin, while, on the other hand, we have 

 in Anacropora the streaming axial layer leading the grovvth, 

 and forming, as in Montipora, the tips of branches, and a 

 further cortical layer formed just as in Montipora. It seemed 

 to me, therefore, that while the fundamental identity in the 

 structure of the colonial skeleton showed that Anacroporce 

 were really Montipores, the presence of protuberant calicles, 

 which might be a slight return to primitive conditions, hardly 

 justified the establishing of a new genus. Comparison with 

 other types and with the undcscribed material in the collec- 

 tion has, however, revealed other characters which are 

 important enough to warrant our retaining the genus, but 

 uniting it with Montipora under a subfamily Montiporinte. 



A\hile, then, the fundamental identity in the structure of 

 the coenenchyma shows that Anacropora has branched off 



* Abh. Nat. Ver. Hamb. xii. p. 46. 



