782 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
not the case in all our specimens. Moreover, the micrometric measurements do not 
appear identical, if the small drawing of Manzoni is exact. It is to be noted that 
figure 6 represents a branch with alternated fascicles. 
A species, also very close, is Idmonea marginata D’Orbigny, 1853, of the Euro- 
pean Senonian. If we consider, for example, figure 8, with its eight tubes to the 
fascicle, the identity is perfect. The zooecial and zoarial dimensions are also identi- 
cal. The only appreciable difference is that the number of the tubes to the 
fascicle is frequently larger than in the Tertiary species. The study of bases and 
ovicells will perhaps permit us some day to make better comparisons. 
This species differs from Idmonea arcuata in the linear form of its zoarium 
and in the distance between the fascicles being double. It differs from Idmonea 
sloani in its larger dimensions and in its transverse section wider than high. 
Occurrence . — Middle Jacksonian: Wilmington, North Carolina (very rare); 
near Lenuds Ferry, South Carolina (rare) ; Eutaw Springs, South Carolina (rare). 
Vicksburgian (Marianna limestone) : West bank Conecuh River, Escambia 
County, Alabama (very common). 
Vicksburgian (Byram marl) : One-fourth mile west of Woodwards, Wayne 
County, Alabama (rare). 
Geological distribution . — Lutetian of Bavaria (Beutler ) ; Auversian at Biar- 
ritz (Canu). 
Plesiotypes. — Cat. Nos. 65355, 65356, U.S.N.M. 
IDMONEA TRIFORATA Canu, 1911. 
Plate 161, figs. 5-24. 
1911 . Idmonea triforata Canu, Les Bryozoaires du Sud-Ouest de la France, Bulletin de la 
Societe geologique de France, ser. 4, vol. 11, p. 452, pi. 8, figs. 13-14. 
Description . — The zoarium is free, linear, bifurcated, with triangular trans- 
verse section wider than high. The fascicles are very salient, irregularly spaced, 
arranged alternately on each side of the median crest and distant from it, pro- 
jecting beyond the zoarial margins; they are formed of three or four zoecia, the 
last of which is turned and opens on the dorsal face and the first is isolated on 
the young branches. The tubes are visible, long, convex; the peristome is quad- 
rangular. The basal lamella is smooth and somewhat convex. 
• Diameter of the tubes 0.20-0.24 mm. 
Distance between the fascicles 0.70-1.00 mm. 
Mmmrenwnts.- w;dth o( thc (asciclcs 0.14-0.16 mm. 
Zoarial width 0.75 mm. 
Variations . — ' This species is exceedingly irregular; the distance between the 
fascicles has no constancy and varies from 1 to 2 times (0.60 to 1.20). On the 
terminal branches the first zooecium of each fascicle is isolated on the median axis 
of the zoarium (figs. 7, 8, 14, 15) and measures 0.30 mm. in diameter. On the 
branches of the base or lower branches the fascicles are regular and complete 
(figs. 12, 13). This double disposition is often visible on the same specimen. 
