40 BRITISH FOSSIL CORALS. 
2. Genus Houarma (p. lvi). 
Horar#a Paristensis. Tab. VI, figs. 2, 2 a. 
Atveouites Partsiensis, Michelin, Icon. Zooph., p. 166, tab. xlv, fig. 10, 1845. 
Corallum composite, and appearmg to have lived fixed to the stem of some Fucus, 
which it incrusted all round, so as to constitute, after the destruction of this extraneous 
body, a hollow cylinder, open at both ends. The lamellar expansion thus rolled round is 
very thin, and its mer or basal surface is covered by an extremely delicate epitheca. The 
calices which occupy the opposite surface, and are consequently placed all round the 
exterior of the above-described cylinder, are infundibuliform, deep, irregularly polygonal, 
surrounded by a prominent margin, and sometimes slightly turned towards one of the 
extremities of the corallum, which was probably its upper end. The fossula is small and 
circular ; its centre is occupied by a fasciculated columella, composed of delicate vertical 
processes, which are quite separated from each other, excepting towards the apex (fig. 2a). 
The vertical section of the corallum, by means of which the composition of the columella 
is seen, shows also that the tissue of the whole mass is uniformly and delicately spongy ; 
no appearance of costa, of septa, or of any radiate structure is perceptible. The diameter 
of the specimen that we have figured is about a line and a half, and the thickness of the 
lamellar expansion that constitutes this cylinder, about half a line; the calices are also 
about half a line in breadth. 
‘This species has been found both in the London Clay at Barton and the Calcaire 
grossier of the environs of Paris. The British specimen represented in our plates belongs 
to the cabinet of Mr. Frederick Edwards. We have examined many of these fossils, but 
owing to the very small size of the corallites, and the extremely delicate structure of their 
constituent parts, we fear that some of their characteristic features may have escaped from 
observation, and we feel much uncertainty respecting the natural affinities of the generic 
division of which it is as yet the only representative. We have not been able to ascertain 
the existence of any tabulz in the interior of the visceral cavity, and therefore it would 
appear to be allied to Poritide rather than to Milleporide ; but it bears great resemblance 
to the latter, and we are inclined to think that, when better-preserved and older specimens 
become known, it will prove to be a tabulated Zoantharia, and if that be the case, there will 
no longer be any reason for distinguishing Holareea from our genus Axopora (p. lix). It 
is therefore only provisionally that we place it in the family of the Poritidee. 
