NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
63 
Fig. 13. — Structure of the avicularium. 
A. Avicularium of Bugula sabatieri Calvet, 1900. 
ar, area. 
b, beak. 
cl, partition. 
ep, epidermis. 
I, leucocytes. 
md, mandible. 
muab, mandibular abductor muscle. 
muab', basal face of the mandible, where the 
avicularium shows the insertion of two ab- 
ductor muscles. 
(After Calvet.) 
muad, mandibular adductor muscle. 
mue, extensor muscle of the avicularium. 
muf, flexor muscle of the avicularium. 
mup, parietal muscles. 
p, peduncle. 
pa, polypidian rudiment. 
rm, mesenchymatous network (or plexus) 
s, cilia of the polypidian rudiment. 
B. Exterior portion of an immersed avicularium ; ar, membranous area ; b, beak ; cmd, 
mandibular cavity ; md, mandible. 
C. Longitudinal section of the avicularium of Schizopodrella ( Scliizoporella ) linearis var. 
hastata Hincks, 1880. (After Calvet, 1900.) 
ce, external layer of the ciliated organ. 
ci, internal layer. 
cmd, mandibular cavity. 
cry, cryptocyst (skeleton).' 
ect, ectocyst. 
epa, avicularian epidermis. 
epb, frontal epidermis of the bryozoid. 
epf, facial epidermis. 
eph, hypostegial epithelium. 
by, hypostege. 
md, mandible. 
muab, mandibular abductor muscle. 
muad, mandibular adductor muscle. 
pa, polypidian rudiment (=eiliated organ). 
D. Enoplostomella synthetica, new species, X 20, showing tremopores transformed into avi- 
cularia. 
E. Section of Cellaria dennanti MacGillivray, 18S7, showing the large avicularian chamber 
and the intermediate zooecia (c). (After Waters, 1904.1 
F. Interzooecial avieularia, with pivot, of Grammella crassimargmata Hincks, 1881. 
G. Curved onychocellarium of Onychocella laciniosa, new species, X 20. 
H. Straight and symmetrical onychocellarium of Floridina antiqua Smitt, 1872, X 20. 
I. Reticulocellarium of Thalamoporella granulata Levinsen, 1909. (After Osburn, 1914.) 
J. Avicularian zooecium of Porella planulata, new species, X 20. 
