358 The American Geologist. June, 1892 
ure, CL rugosun and A, profunda must ultimately stand side by 
side in the same genus. 
Acervularia davidsoni stands somewhat apart from both of the 
foregoing species in a number of particulars. The calyces have 
a sharply defined central pit with explanate margins. In typical 
specimens the floor of the calyx, except in the central pit, is 
almost on a level with the margin; the septa are thick, scarcely 
denticulated, with but a small portion of their edges free; the 
carine are few and clumsy and chiefly developed in the region 
immediately surrounding the central area. Around the edge of 
the central area both primary and secondary septa are conspicu- 
ously thickened, the carine are also developed there better than 
elsewhere, the effect being to produce in polished sections the ap- 
pearance of a bi-areal coral with a central area bounded by a defi- 
nite inner wall. Under the magnifier this wall is never complete. 
The thickened septa and strongly developed carinze never quite 
coalesce, so that the outer area is never, as in true bi-areal corals, 
perfectly shut off from the central space. At the margin of this 
central space the secondary septa all end more or less abruptly, 
and only the primary septa are continued as thin non-carinated 
lameliz into the central area. 
Acervularia davidsoni is certainly con-generic with some of the 
species referred to Acervularia by Edwards and Haime and other 
authors. Whether or not it is generically related to the type 
species of the genus may be left an open question. So long as 
genera are mere artificial creations, without sharply defined nat- 
ural boundaries separating one from another, it will do no violence 
to facts, but will be a matte: of convenience and at the same time 
give effect to a recognizable structural difference, if we keep 4. 
duvidsoné apart from typical forms of the genus Cyathophyllum,* 
and for the present at least retain it in the genus Acervularia. 
Along with A. davidsoni must go Acervularia inequalis Hall and 
Whitfield. Simply as a matter of convenience, but with less con- 
fidence as to the justness of the arrangement, we may add to the 
recognized species of Acervularia the A. profunda Hall, and the 
Cyathophyllum rugosum Hall, as recognized by so many authors. 
The last two may yet, with perfect justice, be separated generic- 
ally from A. davidsont. 
*Dr. Rominger and Mr. W. J. Davis place tuis and related sp-cies un- 
der the genus Cyuthopnayllum. See Geology of Michigan, Vol. IIL, and 
Kentucky Fossi! Vorals. 
