NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
483 
Fig. 186. — Genus Porella Gray, 1348. 
A-Q. Porella cervicornis Pallas, 1766. A. Zoarium, natural size. P>. Zooecia with median 
avicularia, X 20. C. Calcified zooecia, X 20. (A-C after Cal vet, 1904.) D. Operculum with 
its occlusor muscles. E-I. Different forms of the pefistomice. J. Anatomy of a zooecium. 
(D-J after Milne-Edwards, 1838.) coe, caecum of the stomach; est, stomach; gt, tentacular 
sheath ; ph, pharynx ; r, rectum. K. Transversal section. L. Ovicelled zooecia. M. A fossil 
form of frequent occurrence. (K-M after Manzoni, 1877.) N, O. Operculum, X 50, and 
avicularian mandible, X 130. (After Calvet 1900.) P, Q. Orifice, X 50, and avicularian man- 
dible, X 250. (After Waters, 1902.) 
R-T. Porella propinqua Smitt, 1S67. R. Relative arrangement of the ovicell, peristomie, 
and median avicularium. S. Lateral view of a zooecium, X 50. au, avicularian umbo; ov, 
ovicell ; pa, areolar pore ; sp, lateral septula. T. Operculum, X 85, showing a special occurrence 
of the occlusor muscles. (R-T after Nordgaard. 1905.) 
