NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
423 
HOUZEAUINA CALLOSA, new species. 
Plate 54, fig. 11. 
Description. — The zoarium is an Eschara; the partition which separates the 
two lamellae, back to back, is unique. The zooecia are much elongated, distinct, 
rectangular, separated by a very prominent thread; the frontal is smooth, flat, 
garnished laterally with small areolae, of which the two lower are larger than the 
others. The hyperstomial ovicell is imbedded in the distal zooecia; it is salient 
and globular and bears in front a perforated callosity. The median avicularium 
is small, triangular, the beak turned toward the bottom, salient, without pivot, but 
with an opening for the passage of the extensor muscles of the mandible. 
Measurements. — Aperture 
ha= 0.20 mm. 
la= 0.18-0.20 mm. 
Aperture of J ha= 0.15 mm. 
ovicelled zooeciaihz=0.18-0.20 mm. 
Zooecia 
j Lz— 0.70-0.85 mm. 
ifo=0.30 mm. 
Affinities. — This species differs from Houzeauina ornata in the small perforated 
frontal callosity of the ovicell, in its smaller areolae and its larger oral dimensions. 
Only the figured specimen has been found. 
Occurrence. — -Middle Jacksonian: Eighteen miles west of Wrightsville, John- 
son County, Georgia (very rare). 
Iiolotype. — Cat. No. 64109, U.S.N.M. 
HOUZEAUINA LIBRATA, new species. 
Plate 52, figs. 17, 18 ; Plate 55, figs. 1-4. 
Description. — The zoarium is bilamellar, its fronds often claviform. The 
zooecia are indistinct, elongated; the frontal is convex, smooth, garnished laterally 
with some very widely spaced areolae, the lower two of which are the larger; a 
finely granulated pleurocyst is closely united with a thick subjacent olocyst. The 
aperture is imbedded, semilunar, with a proximal border nearly straight; there are 
two very small cardelles placed quite low. The avicularium is median, little salient, 
elliptical; it does not exist on the zooecia provided with two large lower areolae. 
Measurements. — Aperture 
Zooecia 
j A&=0.10-0.14 mm. 
[Za=0.10-0.14 mm. 
fZs=0.60 (max. 0.74mm). 
\lz= 0.30-0.40 mm. 
Variations.- — -The dimensions of the aperture vary very little and oscillate 
around 0.12 mm., nevertheless it is sometimes slightly transverse (0.10 by 0.14 mm.) 
and sometimes a little elongated (0.14 by 0.10 mm.). By rubbing away one face 
we are able to study the interior of the zooecia; the avicularium is indeed that of 
Houzeauina as it results from a development of the lateral areolae, through which 
pass the mesenchymatous fibers which unite it to the zooecia. It establishes a 
phenomenon of balance , of equilibrium between this avicularium and the other 
areolae, chiefly the lower ones, which do not exist on the zooecia deprived of the 
