NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 
139 
As our single specimen is without an ovicell, the generic determination must 
remain doubtful. This species is named in honor of Mr. Wendell C. Mansfield, 
of the United States Geological Survey, who has collected many interesting 
specimens of bryozoa for our study. 
Occurrence .—Miocene (Yorktown formation): miles southwest Reed’s 
Ferry, Virginia (very rare). 
Holotype. —Cat. No. 68627, U.S.N.M. 
CYCLICOPORA(T) GIGANTEA, new species. 
Plate 37, fig. 5. 
Description .—The zoarium incrusts pebbles. The zooecia are distinct, 
gigantic, ogival or hexagonal; the frontal is convex and formed of a tremocyst 
with small scattered pores surmounting an olocyst perforated by very minute 
pores corresponding to the tremopores. The apertura is elongate, elliptical, without 
lyrule or cardelles, with a concave proximal border; it is surrounded by a salient 
peristome, more or less thick and widened. The ovicell is hyperstomial, not 
embedded in the distal zooecium. 
Measurements. —Apertura' 
Aa = 0.30-0.35 mm. 
la =0.30-0.35 mm. 
Zooecia' 
Lz = 1.50-1.60 mm. 
Iz =0.90-1.40 mm. 
Variations .—The micrometric measurements are variable. The tremocyst is 
detachable and finely granular between the pores. The ovicells of our specimens 
are broken and we are therefore unable to classify the species without doubt. 
Occurrence. —Pleistocene: Santa Monica (Tremochal Canyon), California (rare). 
Holotype. —Cat. No. 68628, U.S.N.M. 
Genus AIMULOSIA Jullien, 1888. 
(For description, see Bulletin 106, U. S. National Museum, p. 428.) 
AIMULOSIA ACULEATA, new species. 
Plate 21, figs. 10-14. 
Description .—The zoarium incrusts shells. The zooecia are distinct, separated 
by a furrow, ovoid, wide; the frontal is convex, smooth, perforated laterally by 
small, scattered, areolar pores; it bears on its median line a small avicularium 
very salient, oblique, orbicular, without pivot. The apertura is semilunar, a little 
elongate, with a somewhat concave proximal border; the peristome is thick, 
little salient, and garnished by two distal spines. The ovicell is globular, smooth, 
quite salient, transverse, very widely open in front of the median avicularium. 
Frequently there is a small triangular avicularium at the side of the. apertura. 
„ . a a |k = 0.10mm, 
Measurements .—AperturaC _ , „ 
r ila =0.10 mm, 
Zooecia' 
Lz = 0.50 mm. 
.Iz = 0.45 mm. 
Variations .—In all the species of this genus there is a very great micrometric 
difference between the ancestrular zooecia and the marginal ones. Our measure¬ 
ments are the largest that we have observed. The oral avicularium replaces an 
areolar pore. This is the rule in all the cheilostomatous Bryozoa. This organ is 
nourished in fact from the interior of the zooecia and must necessarily be in 
relationship with the mesenchymatous tissue. This avicularium is inconstant in 
its presence; sometimes it is lacking; sometimes there are two. The irregularity 
