CORALS OF THE LONDON CLAY. 21 
but irregularly crenulated laterally, especially towards the basis. Height four lines ; 
diameter one line and two thirds. 
The only specimen of this species which we have seen belongs to the collection of 
Mr. Frederick Edwards, and is so much filled up with clay at its upper end, that we have 
not been able to ascertain well the form of the columella and the septa; we are, 
however, inclined to think that the columella is slightly compressed, and the septa rather 
thick. 
Turbinoha Prestwichii differs from all the preceding species by its cylindrical form 
and broad convex basis; it differs also from 7 sulcata, T. Divonii, T. pharetra, 
T. Nystiana, T. humilis, and T. Bowerbankiu, by not presenting any vertical rows of 
intercostal dimples; from 7" dispar, 7. costata, and 7. Fredericiana, by having only three 
cycla of costa, mstead of four, and from 7! minor and 7. firma, mm which the intercostal 
dimples are equally wanting, by its sharp-edged costae. 
This remarkable species was found at Haverstock Hull, and appears to be very scarce, 
for Mr. Frederick Edwards, whose collection of London Clay Fossils is extremely rich, has 
only one specimen of it, and we are not aware of its existing m the cabinet of any other 
paleontologist. 
SuB-raMILy oF THE CYATHININ/ (p. xi). 
1. Genus LeptocyaTuus (p. xiv). 
Leprocyatuts evecans. Tab. III, figs. 6, 6a, 6 4, 6c. 
Corallum extremely short, nearly discoidal, and presenting, in the adult state, no trace 
of adherence. Coste distinct from the centre of the under part of the corallum to the 
calice, strong, projecting externally, cristiform, closely set, rather unequal, separated by 
rather deep radiate furrows, and rendered echinulate by the presence of a multitude of 
granulations crowded together (figs. 6a, 64). Calice circular, and regularly excavated 
in the centre. Colwmella not much developed, and delicately papillose. Seta constituting 
four complete cycla, closely set, broad, projecting much above and externally ; very thin 
near the columella, but remarkably thick towards the circumference, and rather unequal 
(fig. 6c); those of the first two cycla nearly equal, and larger than the others ; the tertiary 
ones broader than those of the fourth cyclum, but not so high; all are straight, and none 
adhere together by their inner edge; their sides are covered with granulations, which are 
obtuse towards the circumference of the calice, but become spiniform in the imner part, 
where the septa themselves are slender. Padi corresponding to all the septa (even to 
those of the last cyclum, a mode of structure which is very rare), very thin, slightly 
echinulated, becoming broader as they correspond to younger septa, and appearing to be 
lobated, as in the genus Paracyathus. Height of the corallum, one line ; diameter, three 
lines and a half. 
