NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
7G3 
ERKOSONEA, new genus. 
Greek: ethos, partition in allusion to the ornamentation of the dorsal. 
The zoarium is idmoneiform. The dorsal bears dactylethrae, which appear 
also on the frontal at the bifurcations. The ovicell is globular, spread out between 
three fascicles over the width of the zoarium. 
Fig. 250. — Mesonea, new genus. 
A-G. Mesonea. ( Retepora ) radians Lamarck, 1816. A. Ovicelled zoarium, anterior face. 
(After MacGillivray, 1880.) B. Ovicell, X 25, seen in profile and showing the porous windows. 
C. Transverse section of the ovicell, X 85. (After Waters, 1887.) D. Ovicell with the 
oeciostome (oe), X 25. (After Waters, 1914.) E. Dorsal, X 20. F. Sketch showing details 
of ovicell (o), and porous windows (w), X 20. (After Harmer, 1915.) G. Zoarium, natural 
size. (After Waters, 1914.) 
Genotype.- — Erhosonea semota , new species, Jacksonian. 
The dactylethrae are the aborted tubes, since they are closed by a calcareous 
membrane and do not contain a polypide. They have the same diameter as the 
ordinary tubes and grow in the vicinity of the base of the lower tubes (and not 
at different heights as the tergopores) ; they become branched but rarely. 
These dactylethrae characterize the family Clausidae D’Orbigny, 1853, but 
Gregory noted no idmoneiform genus. 
Tubulipora campicheana Waters, 1887, of which the ovicell is known, must be 
put in a genus close to Erhosonea. The ovicell is very close to that of Mesonea. 
Erhosonea differs from that genus in the presence of dactylethrae instead of 
tergopores. 
ERKOSONEA SEMOTA, new species. 
Plate 133, figs. 1-13. 
Description. — The zoarium is idmoneiform, linear, bifurcated, with oval trans- 
verse section. The fascicles are quite sa lient, scattered. Formed of five zooecia, 
