1909..] IN BRITISH SPECIES OF CORALS. 297 
it comes in while the costs are still high after costal-stage VI. 
(the High Etched) and katagenetic as far as height goes from 
costal-stage VI. towards the low costa of costal-stage VII. So 
far the katagenetic phases of each period have been inconsiderable, 
but the fall in height from costal-stage VI. to costal-stage VII. 
occupies much of the Trochoid shape-stage in the type of P. fittoni. 
In this specimen the peduncle is absent and the costa on first 
appearing are in costal-stage VI., the High Etched stage. ‘The 
earlier stages are seen in the B.M. specimen No. R. 6632, figured 
as Monocarya centralis Mantell by Lonsdale, 1850, in Dixon’s 
‘ Geology of Sussex,’ pl. xviii. fig. 4. This specimen, unfortunately 
damaged in the Trochoid shape-stage, exhibits the earlier and 
later parts and agrees very closely with the type specimen of 
P. fittoni. The costee when first visible are low and wide, but 
rapidly become narrow and high with an ornamentation consisting 
of massed granules (text-fig. 41, A, costal-stages [V.—V.-VI.). As 
far as this first high stage the ornamentation appears as merely 
a roughness and is considered as indicating the Etched Period. 
The Peduncle shape-stage may be looked upon as including the 
Plain and Etched Periods of costal development reduced by 
Tachygenesis to a mere rise in the costa accompanied by a 
roughening of the surface. Whether this is the true explanation 
or not, it is a fact that there is a period of costal elevation which 
has declined before the appearance of the typical granular 
ornament of P. fittons. 
On returning to the type-specimen B.M. no, 48412, it is found 
that the peduncle is broken off, so that the corallum begins in 
the lowest Trochoid shape-stage. The costs when first clearly seen 
are high and narrow (text-fig. 41, B), but rapidly widen and become 
lower (C) until, by the middle of the Trochoid shape-stage, 
they are wide and low and by this time have assumed the typical 
ornamentation of the species, which is very small granules, in- 
dividually separate (text-fig. 41, D', costal stage VII.). At first, 
with the high cost, the ornament appears asa rough ridge, which, 
ag the costa widens, becomes lower, resolves into massed granules 
and finally (costal-stage VII.) into granules individually separate. 
This katagenesis suggests a previous granular anagenesis, but the 
stages on the peduncle do not suggest this; they are etched rather 
than granular, and it is more probable that the granules of costal- 
stage VII. have appeared earlier than thei appropriately shaped 
costa and have become massed and piled in consequence of the 
shape of the costa. 
At about the mid-Trochoid shape-stage, before the coste have 
reached costal-stage VII., the first rejuvenescence occurs. It 
does not, however, interrupt the progress of the costal stages 
by causing recapitulation. This and the next rejuvenescence are 
partial and only affect the convex side of the corallum, which, as 
a whole, is considerably bent. 
Before the second (partial) rejuvenescence, the costa become 
narrower and the granules begin to mass together (text-fig. 41, KH’, 
Proc. Zoou., Soc.—1909, No. XX, 20 
