REPORT ON THE REEF-CORALS. 179 
Porites, for a much larger number of septa frequently occurs. In a very interesting new 
species, Porites mirabilis, obtained by the Challenger from the reefs at Mactan Island, 
this condition is more highly developed than in any of the species from the American 
coast. In this species many very large calicles are found, often at close intervals, among 
the ordinary sized calicles; and in these large calicles three or four cycles of septa are 
present, the fourth cycle being more or less incomplete. In correspondence with this, 
the number of pali is also increased, twelve, sixteen or more being present in these 
cups. 
The most interesting character, however, which is revealed by these specimens is the 
occurrence of the mode of increase by fission in Porites, a condition which has usually 
been regarded as absent in the Poritidze, in which gemmation was constantly observed. 
Fission occurs in not a few of the smaller calicles, and is normal in the larger kind of 
calicles. 
The occurrence at Mactan Island of this very marked species, which presents 
characteristics hitherto observed only in species from the West Coast of America, is an 
extremely interesting fact. The Coral fauna of the West Coast of America is thus closely 
related to that of the Western Pacific districts, not only through this form, but also through 
the new species Dendrophyllia conferta, from Australia, which very closely resembles 
Dendrophyllia surcularis, from the American coasts, and through Stephanaria stellata, 
which is found on the American coasts and in the Sandwich and Fiji Islands. 
Eighteen species of this genus were obtained. 
1. Porites clavaria, Lamarck. 
Porites clavaria, Lamarck, Hist. Anim. sans Vert., ii. p. 270, 1816. 
ii " Milne-Edwards and Haime, Cor., iii. p. 175. 
This species, as pointed out by Pourtalés, is very close to Porites furcata, and it 
becomes a matter of difficulty in some cases to distinguish between them. Apart from 
the size and shape of the corallum, the development of the columella, however, seems to 
be a generally constant character. In Porites furcata the columella is usually scarcely 
visible in the small cell, while in the larger cells of the Porites clavaria it becomes 
comparatively large and but slightly smaller than the pali. 
The specimens in the collection are about 13 cm. high, with diverging, scarcely 
compressed, dichotomously divided branches, 2 em. thick. They are much thicker than, 
but otherwise not unlike, the specimen figured in the Report on the Florida Reefs, pl. xu. 
fig. 7, which Pourtalés has referred to Porites furcata, but the calicles of which, figured 
on pl. xvi. fig. 14, seem to be characteristic ones of Porites clavaria. 
Locality.— Bermuda. 
