1909. | IN BRITISH SPECIES OF CORALS. 287 
of the corallum, some internal characters at a given time will not 
be at the stage of development corresponding with the expected 
synchronous stage of the other internal characters. How far this 
is the case and how far it may be explained in the same way as 
the irregularity in the sequence of the costal ornamentation in 
Parasmilia, further work will show. 
IT. GrowtH-Staces 1n CHALK PARASMILIA. 
The English species of Chalk Parasmilia are attached by their 
proximal ends to foreign objects. That this is an environmental 
rather than an hereditary character seems probable from the 
freedom and varying degrees of fixation in Montlivaltia, pre- 
sumably of one species and from the same horizon and locality ; 
for example, in J. rugosa Duncan *, from the armatus-zone of the 
lias of Honeybourne, E. of Evesham, Worcestershire. It is con- 
ceivable that on a muddy sea-bottom a simple coral would find 
support in the mud around it, sufficient to hold it upright, while on 
a hard bottom it would have need to be fixed. The environment 
of the Chalk sea evidently required the Parasmilia to be attached 
to some hard object. Owing to their fixation, the proximal end 
spreads out to form a surface of attachment. So there is in 
Parasmilia, first a Peduncle shape-stage, next a Trochoid, and 
ultimately, in most, a Cylindrical shape-stage. 
The English species of Parasmilia which have been up till now 
described fall readily into two divisions (see Table, p. 307), ac- 
cording to the nature of the cost at the proximal end of the 
corallum. In one division the proximal end is smooth, that is 
the coste on it are smooth and inconspicuous, or even hardly 
discernible, and only come into evidence in the Trochoid shape- 
stage ; inno stage do they appear granular. In the second division 
the Peduncle or lowest Trochoid shape-stage is granular; the 
granules may appear dispersed irregularly or may fall into definite 
lines and tend to form irregular ridges, and in all cases they have 
become the costal ornament by the time the Trochoid shape-stage 
is reached. The first division contains the species P. centralis 
(Mantell) and P. serpentina Edwards & Haime. The described 
English species of the second division are P. fittont Edwards & 
Haime, P. granulata Duncan, P. gravest Edwards & Haime (Dun- 
can’s interpretation), P. mantelli Edwards & Haime, P. cylindrica 
Edwards & Haime, and P. monilis Duncan (as here interpreted). 
At first sight it is difficult to see any connection between the 
coste of the first and those of the second division. Buta detailed 
examination of the ontogenetic development of the cost renders 
it likely that the primitive costal stages of the second division 
represent the adult costal stages of the first division. At any 
rate, non-granular stages precede the granular in the second 
* P. M. Duncan, 1868, “ British Fossil Corals,” Mon. Pal. Soc. p. 58, pl. xvi. 
figs. 5-15. Compare, for instance, fig. 6 (B.M. no. R. 120438) with fig. 14 (B.M. 
no. R. 12051). 
