324 DESCRIPTION OF CHALK CORALS. 
became colourless. They are believed to be the first proofs of the existence of 
the genus in a secondary formation: whether the English fossil which has been 
assigned to Goldfuss’s Fungia coronula belongs to it, remains to be shown!. 
M. Michelin states that the characters of the lamella in Steph. elegans vary 
with the growth of the zoophyte (Icon. Zoophyt. p. 32). From only three spe- 
cimens of the chalk coral having been examined, it is impossible to hazard an 
opinion respecting the characters of fully perfected or aged structures ; and the 
smallest of them, less than half a line in diameter, differed not in composition 
from the largest, which exceeded very slightly that measurement. The propor- 
tion which the latter specimen (fig. 12) bore to the inner area of M. Michelin’s 
figure 2 a, the part with which a comparison could only be made, was about one 
to five. Supposing therefore that an individual of Steph. elegans of similarly 
limited growth were examined in connection with the English coral, and in that 
state a perfect, structural identity would be evident, still the great difference in 
the dimensions of every component part would clearly justify a specific separa- 
tion. The periphery of the fossil under consideration (fig. 12a) was simple, 
or composed of only lamella extremities, whereas in the foreign species just 
mentioned, it consisted of a curious oval reticulation or union of previously 
subdivided lamelle, the whole constituting in the fine specimen examined a 
nearly vertical boundary of considerable thickness. This outer structure forms 
apparently a leading specific character. In Steph. Italica, though the earliest 
state of the lamellz is essentially similar to that of Steph. elegans and Steph. Mi- 
chelini, yet in the outer zone, which in that instance is in the same plane as the 
inner area, the composite lamellz have two triple subdivisions, while the origi- 
nally simple plates preserve an unchanged character throughout their range. The 
centre of the chalk fossil formed the apex of a regular convex exterior (fig. 12 a), 
and was not marked, in its state of preservation, by any peculiar structure. In 
Steph. elegans the centre is depressed, one of the results probably of age or a 
thickening of the outer boundary ; but in Steph. Italica the whole of the lamellated 
area is very slightly convex or nearly flat. The under surface (fig. 12) was 
obscurely ribbed or radiated, and had a few indistinct punctures or foramine ; 
and presented marked differences, although not well preserved, from both of the 
foreign species. 
‘ Morris's Cat. British Fossils, p. $8 ; Goldfuss, p. 50, tab. 14. fig. 10. 
