BRYOZOA. 441 



STENOPORA TUBERCULATA Prout. 



Fluatra tuberculata Prout. 1859. Trans. St. Louis, Acad. Sci. Vol. I. p. 447. 

 Cyclopora polymorpha Prout. 1860. Trans. St. Louis Acad. Sci. Vol. l,p. 578. 

 C'vclopora polymorpha Prout. 1866. Geol. Sur. 111. Vol. II, p. 421. PI. XXI. fig. 5,5b. 

 PI. XVII, fig. 3 3f. 



Fig. 17. Sections of Stenopora tuberculata Prout x!8. 



(i. Tangential section; l>. Vertical section showing thickness of layers and tabula- 

 tion of zooecial tubes. 



Zoariuni aii expanded crust attached to Brachiopoda and 

 other organisms, frequently attaining a large size by superim- 

 posing of numerous thin layers; sometimes hemispherical, dis- 

 coidal, or laminar, and apparently free, with a rugose epitheca 

 upon the lower side. Surface smooth or with faintly marked, 

 scarcely elevated, clusters of cell apertures but little larger than 

 the average. Apertures polygonal, quite regularly arranged, 

 about ten of the average size in three mm., separated by thin 

 interspaces, spinose at the angles. Zooecial tubes for a short 

 distance prostrate, then curving rapidly to proceed direct to the 

 surface of the layer. Walls thin, somewhat flexuous, often dis- 

 tinctly moniliform. A few mesopores may occur near the center 

 of the clusters mentioned. Diaphragms abundant, perforated, 

 from one-half to their diameter apart. Acanthopores abundant 

 of moderate size, often encroaching upon the visceral cavity. 



The variable form of growth, thicker walls and more numer- 

 ous diaphragms, discriminate this species from S. emaciata, 

 while the more decidedly moniliform walls, thinner zoarial layers, 

 slightly larger zooecia, and smaller acanthopores, separate it 

 from S. cestriensi*. I cannot distinguish from this species 

 Prout's Cyclopora polymorpha, described from the Chester 

 group and propose to unite them as above. 

 55 



