68 G. LE. ANDERSON 
It is evident that if AB (Fig. 8) represents a transverse section, 
there will be four carinae cut and in the order of their appearance 
these are 9, 10, II, 12, carina number g being the oldest of the four, 
and carina number 12 the youngest. Hence the oldest carina in any 
transverse section is the one nearest the center, and they become 
successively younger toward the outer wall. 
Corals with the appearance of an inner wall.—To Strombodes is 
attributed a rudimentary inner wall by Edwards and Haime (Brit. 
Foss. Corals, Intr., p. \xx). It does not possess a true inner wall, 
however, as the coral is composed of superposed lamellae, and the 
fact that it contains no septa renders the presence of an inner wall 
impossible. ‘The appearance of an inner wall in Phillipsastrea is the 
same as that in Acervularia, being formed by pseudo-thecae, and not 
as the true inner wall. Aulophyllum is considered by Edwards and 
Haime (Polyp. Foss. des Terr. Palaeoz., p. 413) to contain an inner 
wall similar to that of Acervularia; hence, it also must be considered 
as not containing a true inner wall. 
In Synaptophyllum (Simp.) and Schoenophyllum (Simp.) the 
appearance of an inner wall is attributed by their author (Bull. 30, 
New York State Museum, Vol. VIII, p. 212), to a thickening of the 
margin of the inner row of dissepiment through which the septa pass 
and extend with free inner borders nearly to the center. In Depaso- 
phyllum!* the upturned outer borders of the tabulae, are fused into the 
lateral area of the short septa forming what appears to be an inner 
wall which is about two-thirds the diameter of the corallite. The septa 
are in no way otherwise connected with the inner wall thus formed 
by the tabulae, and the septa often extend with free inner borders into 
the central area. The wall is thus formed by the tabulae and not by 
the inner borders of the septa which is essential in the true inner wall. 
The inner wall, as found in the coral containing a true inner wall, 
which I shall call “‘bimural corals,’’ is defined as formed originally by 
the inner borders of the long septa. For this reason the long septa, 
with the exception of the cardinal septum, cannot extend into the 
inner central area in “‘bimural corals,” by penetrating the inner wall; 
herein lies the distinction which differentiates it from the Acer- 
vularia type. A longitudinal thin section through the central region 
t Grabau, Geol. and Paleon. of the Devonic Formation of N. Michigan (in press). 
