NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
639 
Fig. 198. — Structure of the tubes and apertura. 
A. Transverse section, X 25, of Mecynoecia cornu ta, new species, a species with club-shaped 
tubes. These appear smaller at the center. B. Transverse section, X 25, of Idmonea marina, new 
species, with the tubes smaller at the center of growth, here laterally placed. C. Longitudinal 
thin section of Idmonea magnireversa, new species, X 25, showing linear space separating tubes. 
D. A branch of Entalopliora cenomana D’Orbigny, enlarged, showing zone of growth. E. The 
zone of growth and basal lamella of Plagioecia ( Diastopora) iatomarginata D’Orbigny. F. 
Sketch showing relations of tentacular sheath and zooecial walls in a cvclostoma tons bryozoan 
(after Calvet, 1900) ; oz, zooecial orifice; d, diaphragmatic orifice; gt, subdiaphragmatic region 
of the tentacular sheath; gt.', super diaphragmatic region of the tentacular sheath; mupd, parie- 
tal diaphragmatic muscles; t, tentacles. G. Surface of Plagioecia prolifera Busk, with orifices 
closed by finely perforated lamella. FI. Surface of Mesenteripora meandrina Busk, 1875, showing 
lamella perforated at the middle. I. Plagioecia sarniensis Hindis, 1880, illustrating lamella sur- 
mounted by a projecting tubule. (Figs. H-J after Busk.) J. Longitudinal thin section, X 12, of 
Hornera concatenata Reuss showing deeply placed lamella. K. Section of Mecynoecia rugosa 
Waters, 1877, illustrating that the lamella is placed where the tube rises free from the zoarium. 
L. Section of Ascosoecia lateralis D’Orbigny preserving a double lamella. (J-L after Waters.) 
