784 B-ULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



IDMIDRONEA, new genus. 



The zoarium is idmoneiform. The dorsal bears firmatopores or canals of 

 reinforcement. 



Genotype. Idmidronea 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 Idmonea, 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 species. 



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 zooecia ; 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 Idmidronea mamUari-s Lonsdale, 1847, in the rotate form of its 

 zoarium and in its nonsalient fascicles, and from /. culter in its fascicles, which are 

 more scattered, more distinct, never adjacent on the median line. 



Occurrence. Middle Jacksonian (Castle Hayne limestone) : AVilmington. 

 North Carolina (rare). 



Cotypes.Qnt. No. 65359, U.S.N.M. 



Measurements. 



