INTRODUCTION. 13 
Amongst essential columella the styliform may end in a cylindrical and pointed 
process, or in a more or less compressed and blunt, which may project even higher than 
the septa, or in a bulbous termination marked by ridges corresponding with large septa ; 
or the organ may be angular in transverse outline, and project but slightly above the 
bottom of the calicular fossa. The styliform columellz may be studied in the genera 
Turbinolia, Synhelia, Stylophora, Acosmilia, Stylosmilia, Stylina, Holocenia, Stylocenia, 
Astrocenia, Stephanocenia, Holocystes, Cyathoxonia, Syringophyllum, and Phallips- 
astrea. They are nearly solid, spring from the base, and may or may not be attached by 
processes to the septa. Very visible in well-preserved specimens, these columelle are 
readily destroyed by rolling, and cannot then be distinguished except by sections. In 
many species, especially in the Astroceniz, the columella appears to be very large in 
certain fossil Conditions ; but this appearance arises from a mechanical adhesion of calca- 
reous particles to the outside of the columella and between the inner ends of the septa. 
There are examples of styliform columella (Plate IX, figs. 3, 6, 10). 
The lamellar form of essential columella (Plate I, fig. 6; Plate IV, fig. 14) may occur 
in circular, elliptical, or in elongated calices. It is seen as a sharp edge, generally 
at the bottom of the calicular fossa, and may be in contact both with septa and pali. Its 
sides are occasionally ornamented with granules. In the genus Madrepora, and in some 
species of Solenastrea this lamellar columella does not really exist, but is simulated either 
by the junction of opposite septa or by the irregular development of neighbouring septal 
ends. ‘The true lamellar columella is not formed by septa, but springs from the base of the 
corallum. 
The fascicular columella is a very complicated organ. In its simplest form it is a 
bundle of rods coalesced laterally, adherent below, and rounded at the free calicular 
surface. } 
This structure is well seen in the genus Azopora (Plate VII, fig. 14), andin an Austra- 
lian fossil, the Conosmilia anomala’ (nobis). Here are two riband-shaped processes arising 
from the base, and projecting in the calicula fossa; each is simply twisted five or six 
times, so that the riband’s edge takes on a spiral form; this is the simplest form of the 
common fascicular columella, and in Plate I, fig. 13, several processes, really riband- 
shaped, but much twisted, are seen in lateral contact, the whole forming the columella. 
The number of the processes varies in different species, and it is tolerably constant in 
certain forms ; the processes, were they untwisted, would form a number of flattened and 
lamellar columellz in lateral apposition. The septa and pali do not contribute to their 
formation. ‘Ihe calicular surface of the fascicular columelle may be papillary, or even 
twisted ; and it most frequently resembles the arrangement of the central portions of the 
flowers of certain Composité ; hence the term “ chicoracé,” which is most significant and 
explanatory of the appearance of the calicular surface of the columella in the genus 
Caryophyllia. 
1 Ann. Mag. Nat. Hist.,’ ser. 3, vol. xvi, pl. viii, fig. 4e. 
