NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
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a more or less widened cone and always witli the apex below. It maintains its 
normal position by the aid of long articulated filaments called vibracula, which are 
thus organs for the maintenance of stability. 
Fig. 64. — Subfamily Lunulariidae Levinsen, 1909. 
A-C. Lunularia capulus Busk, 1884. A. Zoarium, natural size. B, C. Outer (celluliferous) 
and inner faces of the zoarium, X 25. (After Busk, 1884.) 
D-F. Lunularia patelliformis Maplestone, 1903. D. Inner face, X 25. E, F. Vibracular 
cavity and vibraculum, X 25. (After Maplestone, 1903.) 
G, H. Lunularia repandus Maplestone, 1903. Vibracular cavity and vibraculum, X 25. 
(After Maplestone, 1903.) 
I. Internal cast of Lunularia liagenowi Bosq, 1851. ( After Beissel, 1865. ) 
J. Vertical section of Lunularia, traversing an oyicelled zooecium. ov, ovicell; s, septula; 
zoar, zoarium ; zp, proximal zooecium. 
K. Vertical fracture of Lunularia tintinabula, new species, X 10, showing that the zoarium 
is composed of plurilamellar segments commencing at the center or at a bifurcation. 
The choice of a substratum by the larvae is instinctive but not infallible. 
Often they affix themselves on very heavy objects on which, nevertheless, the zoa- 
rium developes. ( Reptolunulites of D'Orbigny.) 
