PLATE XVIII. 

 CALLOPORA. 



(Page 588.) 

 Callopora elegantula, Hall. 



Figs. 1, 2. Specimens, natural size. 



Fig. 3. A fragment of a specimen fractured so as to show the cell 

 tubes. x6. 



Fig. 4. An enlargement of the surface, showing the form and arrange- 

 ment of the cell apertures and interapertural openings. 

 Several of the apertures on the lower portion of the figure 

 have opercula. 



Fig. 5. An enlargement of one of the apertures, showing the oper- 

 culum. xlOO. 



Figs. 6, 1. These sections show the tabulated cell tubes and the 

 tabulated mesopores. xl8. 

 Niagara group. JOockporty JV. Y. 



CALLOTRYPA. 



(Page 551.) 

 Callotkypa uNispiis^A, Hall. 

 Fig. 8. A specimen, natural size. 



Fig. 9. An enlargement showing the form and arrangement of the 

 cell apertures and interapertural pits, and the prominent 

 node at the base of each aperture. xl8. 

 Fig. 10. An enlargement of one of the cell apertures and its accom- 

 panying node. x54. 

 Fig. 11. A thin vertical section, showing the internal structure. xlS. 

 Lower Helderberg group. JVew York. 



Calloteypa macropoea, Hall. 

 Figs. 12, 13. Groups of Bryozoa, among which are several of this 



species. 

 Fig, 14. A portion of a branch. xl8. 



Lower Helderberg group. JVew York. 



654 



