INTRODUCTION. 1 3 



Amongst essential coluraellse 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 columellse may be studied in the genera 

 Turlinolia, Synhelia, Stylophora, Axosmilia, Stylosmilia, Stylina, Iloloccenia, Styloccenia, 

 Astroccenia, Stephmioccenia, Holocystes, Cyatlioxonia, Syringophyllum, and FUillips- 

 astrcea. 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 columellas are 

 readily destroyed by rolling, and cannot then be distinguished except by sections. In 

 many species, especially in the Astrocosnies, 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 columellse (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 Solenasircsa 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 Awopora (Plate VII, fig. 14), and in an Austra- 

 lian fossil, the Conosniilia anomald (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 columellse in lateral apposition. The septa and pali do not contribute t(j their 

 formation. The calicular surface of the fascicular columellee may be papillary, or even 

 twisted ; and it most frequently resembles the arrangement of the central portions of the 

 flowers of certain Compositse-; hence the term "chicorace," which is most significant and 

 explanatory of the appearance of the calicular surface of the columella in the genus 

 Caryopliyllia. 



1 ' Ami. Mag. Nat. Hist.,' ser. 3, vol. xvi, pi. viii, fig. Ae. 



