578 



Report of the State Geologist. 



region the cell walls are very thin, and the diaphragms are com- 

 paratively distant. In the peripheral region the walls are much 

 thickened and the diaphragms are much more numerous ; surface 

 with slightly elevated monticules, having cell apertures a little 

 larger than those on other portions of the frond. 



Deka^yia, Edwards and Haime. 

 (Mon. de Pol. Foss. de Terr. Pal , p. 127. 1851.) 

 Type, Dekayia aspera, Edwards and Haime. 



Zoarium ramose, branches cylindrical or flattened ; cells 

 tubular, polygonal, arising from an imaginary axis at the center 

 of the branch, gradually diverging until near the surface, when 

 they abruptly, turn outward. In the axial region the walls are 

 very thin, and the diaphragms are very infrequent or entirely 

 wanting. In the peripheral region the cell walls are much 

 thickened and the diaphragms are of moderately frequent occur- 

 rence, the walls becoming moniliform. The cell apertures are 

 polygonal and have numerous spines (acanthopores) at the angles; 

 surface with numerous maculae, the cell apertures of which are 

 larger than those on other portions of the frond. 



142 



143 



Fig. 141. Dekayia devonica, natural size. 



Fig. 142. Vertical section, xl8. 



Fig. 143. Surface, xl8. 



Fig. 144. Transverse section, x36. 



Heterotrypa, ]S^icholson. • 

 (Pal. Tab. Corals, p. 291. 1879.) 

 Type, Heterotrypa mammulata, Nicholson. 

 Zoarium consisting of large lobate or frondescent expansions; 

 cells tubular, polygonal, arising from an imaginary axis, gradu- 



