PLATE XY. 



MiCHELINA (PlEURODICTYUM) CONVEXA. 



Miohelina cottvexa D'Orbigny. Prodrome de Palfeontologie, Vol. 1, p. 107. 



" " Edw. -Haime. Polyp. Foss. des Terrains Palfeozoiqiies, p. 351, pi. 16, f. 1. 



" " Billings. Canadian Journal, New Series, Vol. IV, page 112. 1859. 



Fig. 1. The weathered summit of a specimen presenting principally the apertures of the large 

 cells which preserve the strife upon their inner surfaces, with diaphragms nearly all 

 complete. 



Fig. 2. The weathered surface of a turbinate form, showing the partial and more or less complete 

 convex diaphragms. 



Fig. 3. The summit of a larger individual, showing the variable size of the cells, the interior stria 

 tion and the more or less complete convex diaphragms. 



Fig. 4. An obliquely vertical section, produced by wear and weathering, and preserving the longi- 

 tudinal striae, the connecting pores and the margins of the diaphragms. 



Fig. 5. A vertical section, cutting the cells longitudinally, and showing the vesicular structure of 

 the diaphragms. 



These figures present illustrations o£ the common forms of the species as they 

 occur in the Upper Ilelderberg limestone in New York, Ontario, Ohio, Michigan, and 

 at the Falls of the Ohio in Indiana and Kentucky. 



