Tabulate Corals ivith Existing Species. 361 



one with the Pocilloporidcej although Edwards and Hairae 

 placed it in the same family with the latter. 



In the ' Report on the Zoophytes of the U.-S. Exploring 

 Expedition,' 1846, p. 509, Professor Dana instituted the 

 family Favositidce^ in which he included three subfamilies : — 

 1st, Aheojwrina^j including the genus Alveojjora ; 2nd, Favo- 

 sitince^ embracing StylopJiora^ Pocillopora^ Seriatipora, with 

 Favosites and other extinct genera; 3rd, Helioporince^ for 

 Heliopora^ Millepora^ Heliolites : this family was placed 

 next to the Poritidce. Although more recent discoveries have 

 shown that this arrangement is incorrect in several points, it is 

 nevertheless much nearer correct than the classifications of 

 Edwards and Haime and Agassiz. In thus bringing Alveopora 

 and Favosites near together. Prof, Dana made a very important 

 step in advance, and one that has unfortunately been lost sight 

 of, or overlooked, by recent writers, and most unfortunately by 

 Edwards and Haime, by whom these genera are very widely 

 separated. In describing the genus Alveojjora, Professor 

 Dana gives, as one of its characters, " transverse septa 

 remote;" and on plate 48. fig. 3, d, of his 'Atlas,' from 

 which the accompanying cut has been copied, he figured a 

 vertical section of Alveopora spongiosa^ in which the transverse 

 septa are well shown (fig. 1, a). In this species the walls of 

 the cells are exceedingly thin and pierced by numerous large 

 openings, often leaving a mere skeleton of a wall. The 

 transverse septa, although thin, are perfectly developed and 

 imperforate, completely closing the cells at intervals of about 

 '05 to "20 of an inch, varying even more than this in some 

 parts of the coral, but not more than do many species of 

 Favosites. Moreover the septa in many adjacent cells are 

 situated at the same level, giving the coral the appearance of 

 being divided into successive layers by broad, thin transverse 

 plates. This appearance is due merely to the thinness and 

 porosity of the walls and coincidence of the plates. The same 

 arrangement of plates is found in the Silurian genus Dania^ 

 which, however, is said to have imperforate walls. 



The structm-e of the walls in the tabulated genus Koninckia^ 

 from the Cretaceous, is very similar to that of Alveopora, 

 Moreover the latter, like Alveopora (fig. 1, h), has vertical 

 rows of spine-like points, representing the twelve radiating 

 septa. In some, if not all, s})ecies of Favosites the septa Avere 

 likewise represented by just such rows of slender points. And 

 the same is true of other extinct genera belonging to the same 

 group. Whether all the species of Alveojjora have complete 

 transverse septa is uncertain ; for they appear to have been 

 generally overlooked by the describcrs. Edwards and Haime 



Ann. d: Mag. y. Hist. Scr.4. Vol.lx. 25 



