CORALS OF THE LONDON CLAY. 19 
up, if they had corresponded to septa belonging to the third cyclum. All the septa are 
very thin, almost glabrous, exsert, and terminated by a regularly arched apex, rising more 
or less, according to the cyclum to which they belong. Height not quite a line and a half ; 
diameter of the calice two thirds of a line. 
This Coral is one of the smallest of the genus Turbinolia, and is indeed usually even 
smaller than the species designated by the name of 7urdinolia minor, for which it may very 
easily be mistaken ; its characteristic features can only be seen with the help of a lens, 
but when sufficiently magnified, the appearance of its walls will make it immediately 
recognisable ; for in 7. minor the coste: are very thick, crenulated laterally, and the inter- 
costal furrows do not present any dimples, whereas in 7. Awmlis these dimples are well 
marked, and the costs are thm. These two species are the only ones of the genus that 
have apparently but five tertiary systems, and their diminutive size contributes also to 
make them not easily recognisable. 
Turbinolia humilis is found in the London Clay at Barton, where it appears to be 
abundant. We are indebted to Mr. F. Dixon and Mr. Frederick Edwards for the 
specimens in our possession. 
6. Tursrnouta minor. ‘Tab. II, figs. 5, 5 @, 5 4. 
TURBINOLIA MINOR, Milne Edwards and J. Haime, Annales des Sc. Nat., 3™° série, vol. ix, 
p. 239, 1848. 
Corallum of a cylindrico-conical form, rather short, and very obtuse at its basis. Coste 
very thick, closely set, and not very prominent ; those of the first and second order par- 
ticularly thick near the basis; the outer edge of all very obtuse, and their sides delicately 
crenulated. Intercostal furrows very narrow, linear, and presenting no trace of the dimples, 
which are so apparent in the preceding species. The form of the costa is particularly well 
marked near the calice (fig. 5 4), the lateral crenations of which are sometimes so developed 
near the basis, that they assume a crispate appearance ; in other specimens they are scarcely 
visible, but the variations met with in the form of these parts are never such as to make 
them resemble the costa of 7. humilis. Calice very deep. Columella cylindrical, slender, 
and exsert. Sepa belonging to three cycla, and appearing to form only five systems, 
although there are in reality six systems as usual; only in two of these there are no 
tertiary septa, and the secondary septa are of the size of the other tertiary ones, but 
correspond to secondary costs, the development of which are normal (fig. 54). All the 
septa are thin, exsert, and slightly granulated on their lateral surfaces ; the secondary ones 
are nearly as large as those of the first order, but those of the third cyclum are much 
smaller. This species is always remarkably small; it is not more than a line and a half 
high, and two thirds of a line in diameter. 
