STUDIES IN THE DEVELOPMENT OF CERTAIN PALEO- 
ZOIC CORALS 
G. E. ANDERSON 
Columbia University, New York 
ON THE ORIGIN AND DEVELOPMENT OF THE INNER WALL 
Certain Paleozoic corals have been characterized by their authors 
as containing an inner wall which divides the corallite into an inner 
central and an outer annular area, the latter extending between the 
two walls. It has also been observed that in a number of these genera 
the septa extend to the center, penetrating the supposed inner wall, 
while in others the septa terminate in the inner wall itself. ‘The genus 
Acervularia is a type of the former and Craspedophyllum' of the 
latter. The character of the inner wall in the two types is such that 
they can readily be differentiated even in a very cursory examination. 
While both genera have been considered to contain an inner wall, 
Edwards and Haimes as early as 1850 (Polyp. Foss. des Terr. Paleoz.) 
differentiated the two types by noting that the internal structure of 
Eridophyllum, which is of the Craspedophyllum type, differed from 
Acervularia in that the septa terminated in the inner wall, while in 
the latter the septa extended through the inner wall into the inner 
central area. ‘They do not record having noted any difference in the 
structure of the inner walls themselves in the two genera. 
Thin sections reveal the fact that the structure of the two types 
of wall are quite different and that they have an entirely different 
origin. The inner wall in the Craspedophyllum-Eridophyllum 
type is of a similar nature in texture and thickness to the septa, and 
occupies but a small central circular portion of the corallite. 
In Craspedophyllum the diameter of the inner wall is about one- 
sixth to one-fifth that of the corallite. In the normal adult of this 
genus the inner wall has one opening, connecting the central area 
with the cardinal fossula. This gives to the inner wall the shape 
z Equivalent to Thomson’s Crepidophyllum, which term is used by Canadian 
paleontologists. 
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