292 DESCRIPTION OF CHALK CORALS. 
solicited to the genus had its reception depended on Aps. cerebriformis, or if M. 
Michelin’s delineations of Aps. dianthus had not displayed structures much more 
analogous to those of Mr. Dixon’s fossil. M. De Blainville in his brief notice of 
that species says, it is “‘ trés remarquable par la forme et le dessin de ses crétes, 
qui portent les cellules 4 tout leur bord externe”’ (loc. cit.) ; and this peculiarity 
is fully expressed in fig. 4 c of the ‘ Iconographie Zoophytologique ;’ the actual 
crest, moreover, being a continuous layer without tubular apertures. By refer- 
ence to Tab. XVIII. A. figs. 9,9, 9c, illustrative of these remarks, a general agree- 
ment, as respects plan of growth, will be found with Aps. dianthus, also in the 
sides of the branches being completely beset with mouths ; a medial line likewise 
occurs, though less prominently than in M. Michelin’s figure 4c. An enlarged 
portion (fig. 46) of fig. 4 a (Icon. Zoophyt. pl. 55) displays, if rightly understood, 
horizontally or obliquely connected branches, though a further magnified repre- 
sentation (fig.4¢) shows merely simple disconnected ramifications. The English 
fossil had very generally similar, free branches (fig.9) ; but one specimen (fig. 9a), 
evidently of most irregular growth, gave also equivalent transverse junctions. 
These extensions, whether normal or not, differed however in both cases from 
the dorsal layer of Aps. cristata not only in position, but in being occupied 
equally with the branches by visceral tubes, whereas in the species just men- 
tioned there is not a single aperture in the uniting structure. No information 
has been published, it is believed, respecting the nature of the mouths or the 
characters of the internal structure of Aps. dianthus. In the English coral the 
openings bordering the crest of the lamelliform branches (fig. 9b) are large, or 
equal to the transverse dimensions of the tubes, with sometimes a slightly pro- 
jecting margin ; but on the sides of the branches they are wholly depressed as 
well as contracted to a mere pore and occasionally obliterated, the periphery of 
the cavities being defined by a network of ridges (fig. 9c). It is not quite clear 
whether the dorsal surface of Aps. dianthus is provided with apertures, but in the 
subject of this notice (fig. 9d) they are as abundant in that portion as in any other. 
Internally (figs. 9 e, 9f) Mr. Dixon’s coral is wholly composed of tubes, those ad- 
jacent to the back of the branch ranging nearly parallel to it, and in the line of 
outward extension of the coral, the mouths opening also in the back itself; while 
the cavities composing the chief part of the branch incline towards the crest 
terminating successively on the sides, and their apertures occupy the entire sur- 
face, so that no portion of the tubes is visible externally. Small pores were 
abundant in a slightly worn-down fragment (fig. 9e) ; they were however con- 
