784 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
IDMIDRONEA, new genus. 
The zoarium is idmoneiform. The dorsal bears firmatopores or canals of 
reinforcement. 
Genotype. — 1 dmidronea coronopus Defrance, 1822. 
Range. — Lutetian- Jacksonian. 
The firmatopores are small canals, very thin and numerous, which develop on 
the dorsal of the zoarium in great thickness. They are parallel and very long, for 
we have followed them throughout the length of a branch. In a longitudinal 
section they appear somewhat intermingled, for it is absolutely impossible to 
prepare a section in a position exactly parallel to their general direction. On the 
dorsal they appear as very small, longitudinal striations extremely numerous and 
quite close together. In Iclmonea , on the contrary, the longitudinal striations are 
much more scattered and limit the tubes themselves which are entirely visible. The 
tergopores are much larger. The firmatopores are evidently intended to reinforce 
the consolidation of the branches. It is almost certain that they indicate a zoarium 
which is horizontal or arranged in a much expanded bush-like shape. All of the 
branches are not provided with firmatopores and the generic classification is then 
very difficult. 
We have not found the ovicell, so the place of this genus in the family of the 
Tubuliporidae is naturally hypothetical. 
IDMIDRONEA ROSACEA, new speciea. 
Plate 132, figs. 11-15. 
Description. — The zoarium is supported on a more or less expanded base 
which forms a trunk of greater or less size ; the branches are directed horizontally 
in all directions from the center like the petals of a rose. They are bifurcated and 
their section is triangular. The fascicles are very little salient and bear only two 
or three zooeeia; they are alternated on each side of the median line. The tubes 
are invisible; the peristomes are thin, round, or rectangular. On the dorsal the 
firmatopores are arranged longitudinally; they are rather large and their visible 
orifice, which results from abrasion, is polygonal. 
Diameter of the tubes 0.16 mm. 
Width of the fascicles 0.16 mm. 
Distance between the fascicles 0.32 mm. 
. Width of the branches toward the base 2.00 mm. 
Affinities. — This superb species is rather rare. It is remarkable because it 
appears to be formed of two symmetrical zoaria arranged horizontally on each 
side of the ancestrular center. 
It differs from I dmidronea maxillaris Lonsdale, 1847, in the rotate form of its 
zoarium and in its nonsalient fascicles, and from I. cutter in its fascicles, which are 
more scattered, more distinct, never adjacent on the median line. 
Occurrence. — Middle Jacksonian (Castle Hayne limestone) : Wilmington. 
North Carolina (rare). 
Cotypes. — Cat. No. 65359, U.S.N.M. 
Measurements . — 
