THE BRYOZOA BASSLER. 379 



Fig. 13. — A branching species, Zonopora eottaldina D'Orbigny, magnified, 

 from the Cretaceous of France, with the zooecial apertures and mesopores ar- 

 ranged in regular zones. 



Fig. 14. — Magnified view of a solid ramose species, Multicavea magnified 

 D'Orbigny, from the Upper Cretaceous of France. 



Fig. 15. — A solid ramose bryozoan, Tretoeiicloecia attcnuata Ulrich, x 8, 

 from the Lower Eocene (Midway an) of Arkansas, with mesopores and a zoa- 

 rium as in the Trepostomata, but possessing the ovicell (broken) of the Cyclo- 

 stomata. 



Fig. 16. — A composite zoarium, Centronea (Multitubigera) micropora Reuss, 

 enlarged, from the Eocene rocks of Northern Italy. 



Fig. 17. — A very common, ; inple ramose species of Cyclostomata, Mecynoecia 

 proboscidca Milne-Edwards, x S, from the Tertiary (Vicksburgian) rocks of 

 Alabama. 



Fig. 18. — Another branching species, Spiropora majuscula Canu and Bassler, 

 x 8, from the Eocene of South Carolina, showing the arrangement of the aper- 

 tures in regular rows. 



Plate 4. 



Structural features of the Cyclostomata. 



Fig. 1. — Zoarium of Stomalopora parinpora Canu and Bassler, x 12, from the 

 Eocene rocks of Mississrppi showing the orbicular protoecium from which the 

 first zooecium or ancestrula develops. 



Fig. 2. — Drawing of a recent, bilinear, encrusting species, Peristomoecia 

 (Stomatopora) divergent Waters, enlarged, in which the free portion of the 

 tube enlarges to form the ovicell. 



Fig. 3. — A recent encrusting species, Oncousoecia (Tubulipora) lobulata 

 Hincks, magnified, with the axis of the ovicell parallel to the tubes. 



Fig. 4. — An ovicelled branch, x 6, of a fossil species, Idmonea grallator Canu 

 and Bassler, from the Eocene rocks of Alabama, showing the ovicell on the 

 celluliferous side. 



Frc 5. — Ovicelled example of Tervia, irregularis Meneghini, x 6, illustrating 

 the position of the ovicell on the dorsal, noncelluliferous side, characteristic 

 of the family Terviidae. 



Fig. 6. — Ovicelled zoarium, x 10, of the recent species Tubulipora flabellaris 

 Fabricius. 



Fig. 7. — The characteristic ovicell of the family Macroeciidae Canu, x 6, in 

 which the oeciostome or opening of the ovicell is unusually large. 



Fig. 8. — Basal side of an ovicelled zoarium of a discoidal species, Discoci/tis 

 eudesi Michelin, x 3, from the Cretaceous rocks of France. The ovicells (some 

 of them broken) form a regular circle about the base. 



Fig. 9. — A portion of the jointed colony of Crisia showing the characteristic 

 ovicell in the family Crisiidae. 



Fig. 10. — A common recent and fossil bryozoan, Mecynoecia (Entalophora) 

 probosc-idea Milne-Edwards, x 6, illustrating development of the ovicell parallel 

 to the tubes. 



Fig. 11. — A recent encrusting species Plagioecia patina Lamarck, x 6, exhibit- 

 ing position of ovicell at right angles to the direction of the zooecia, characteris- 

 tic of the family Plagioeciidae. 



Fig. 12. — The ovicell of Partretocycloecia porosa Canu and Bassler, x G, from 

 the Eocene rocks of South Carolina, showing characteristics of the Tretocycloe- 

 ciidae, a family of the Cyclostomata with mesopores and other features resem- 

 bling the Trepostomata. 



