new Species of Monticuliporoid Corals. 341 
3. Dekayella* robusta, Foord. (PI. XII. figs. 2-2 d.) 
Corallum ramose, frequently branching. Branches thick, 
usually cylindrical or subcylindrical, sometimes compressed. 
Surface covered with small but tolerably conspicuous mon- 
ticules, situated about 3 millimetres apart, and bearing cells 
of a somewhat larger size than those in the intermediate 
spaces. ‘The apertures of the corallites are polygonal in out- 
line, and in places where the surface is well preserved some of 
the larger of the spiniform corallites may be seen with a hand- 
lens. Of the larger corallites about four occupy the space of 
1 millimetre, of the smaller about five. 
Microscopic characters,—Tangential sections reveal clearly 
the dimorphic character of the corallum, which is provided 
with two kinds of tubes, large and small; both are of poly- 
gonal form, and their outline is inflated in many places by 
the occurrence of numerous spiniform corallites. ‘l'hese also 
are of two kinds: the larger are usually situated at the angles 
formed by the junction of four or five cells,’and fill a space 
quite as great as that occupied by some of the interstitial 
cells; the smaller are generally found to be in the substance 
of the cell-walls, about midway between two angles. The 
spiniform corallites form a very conspicuous feature in tan- 
gential sections of this species, and give to such sections a 
highly characteristic appearance. Under a moderately high 
power traces of the original walls of the corallites may be 
discerned in tangential sections; but as a rule this structure 
appears to have been destroyed in the process of fossilization. 
In longitudinal sections the two sets of tubes are clearly 
brought into view. In the larger ones there are numerous 
horizontal, sometimes slightly oblique, tabula, situated at 
from one half to one tube-diameter apart ; they begin in the 
axial region of the corallum, and are about equally developed 
in their course from thence to the peripheral region. ‘he 
smaller tubes do not differ in the character of their tabulation 
from the larger ones, except that the tabule in the former are 
a little more frequent than they are in the latter. There is a 
feature worthy of note in the structure of the walls of this 
species, and that is a periodic inflation, which reminds the 
* Mr. E. O. Ulrich (“ American Paleozoic Bryozoa,” Journ. Cincinnati 
Soc. Nat. Hist. vol. v. p. 155, 1882) constituted this genus for the recep- 
tion of forms “ more nearly allied to Dekayia, Edwards and Haime, than 
to any other genus of the Monticuliporide,” but differing therefrom “ in 
having the tube-walls in the mature region of the zoarium thicker, in 
having numerous interstitial tubes, and, instead of one, two distinct sets of 
spiniform tubuli” |=‘ spiniform corallites” of Nicholson}. This last is 
stated by Mr. Ulrich to be the most important character of the genus. 
