NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
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Fig. 123. — Anatomy of the Microporellae. 
, A-E. Microporella ciliata Pallas, 1766. A. Profile view of free larva, X 75. B. Free 
larva, oral view, showing the large radiating elements of the oral mesoderm, X 50. C. Free 
larva, aboral view, showing the radiating aspect of the calotte, 50. (A-C after Barrois, 1877.) 
c, corona ; 
cal, calotte (terminal bud) ; 
CD, digestive cavity; 
ce, obscure part between the two branches of 
the stomach ; 
mi, aboral mesoderm ; 
ms, oral mesoderm ; 
O, ciliated cleft ; 
oc, oculiform points; 
pin, pharynx ; 
RV, border of the calotte. 
D. Median sagittal section of an embryo in one of the last stages of development. (After 
Calvet, 1900.) E. Ancestrula and two zooecia. The original aperture of the ancestrula, which 
is surrounded by spines, is almost closed to a pore, X 55. (After Levinsen, 1909.) 
F-N. Microporella malusi Audouin, 1826. F. Median sagittal section of an embryo just 
before it emerges. (After Calvet, 1900.) In the course of the neuro-muscular bundles passing 
from the central nerve organs to the pyriform organ some cellules are seen. The internal sack 
has a simple form almost regularly cylindrical. 
c, mantle; 
cal, calotte (terminal bud) ; 
co, corona ; 
d, tampon or inner sac ; 
ect, ectoderm ; 
epe, ectoderm thickening; 
epm, mesoderm thickening; 
fc, ciliated cleft ; 
fum, neuro-muscular bundle; 
one, central nervous organ of the embryo ; 
pfse, sub-ectoderm nerve plexus ; 
pplv, papilla of the vibratile plume ; 
si, internal sac; 
sgs, superior glandular system ; 
sqi, inferior glandular system. 
G. Longitudinal section of a bryozoid. (After Calvet, 1900.) 
caec, stomachic caecum ; 
ci, incubation cavity ; 
cry, cryptocyst, or skeleton ; 
d, diaphragm ; 
epli, hypostegal epithelium ; 
epi, spine; 
fe, central funicular cord ; 
fl, lateral funicular cord ; 
gn, nervous ganglion; 
gt, sub-diaphragm region of the tentacular 
sheath ; 
gt', subdiaphragm region ; 
hy, liypostege; 
mud, dilator muscles of the incubation cavity ; 
mugr, large retractor muscle ; 
mur, retractor muscles of the frontal walls 
of the lower ovicellarian vesicle ; 
oes, esophagus ; 
op, operculum ; 
os, zooecial orifice ; 
pme, median frontal' pore ; 
py, pyloris ; 
re, rectum ; 
t, tentacles ; 
rot, lower ovicellarian vesicle ; 
vos, upper ovicellarian vesicle. 
H. Zooecia, X 50. (After Waters, 1903.) I. Ancestrula. The frontal membrane (fm) 
is typically flustrine and bears an opercular valve; its calcareous margin bears ten spines, of 
which three are oral spines (op). The brown body (bl) may be noted. (After Harmer, 1902.) 
J. Frontal pores, X 250. (After Waters, 1914.1 K. Aperture, X 100. (After Levinsen, 1909.) 
L. Basal view of a zooecium which has lost its polypide. (After Harmer, 1902.) 
l>, polypide bud ; occl, opercular muscles ; 
bb, brown body; p. c„ dietellae; 
corn, cornicula ; z, neighboring zooecia. 
cs, compensatrix opening by the ascopore 
(m. p.) ; 
