478 GEOLOGICAL SURVEY OF IOWA. 



Fig. 7 a. Part of a large hemispheric mass, showing several young cells, some 'nearly 

 circular : natural size. 



Fig. 7 b. Transverse section of a cell, enlarged, from a polished surface. The inner wall 

 is not defined, and many of the rays are continuous to the centre of the 

 cup. 



Fig. 7 c. A- portion of a cell, enlarged, showing the denticulated rays. 



Geological formation and locality. In limestone of the age of the Ha- 

 milton group of New- York : Independence, Iowa. 



CLADOPORA (HALL). 



" CORAL ramose or reticulate ; branches cylindrical or 

 slightly compressed, terminations terete : coral composed of 

 a series of tubes or cells radiating equally on all sides from 

 the axis, and opening upon the surface in rounded or suban- 

 gular expanded mouths ; cells more or less closely arranged, 

 but not always contiguous, and apparently destitute of septa 

 or rays". Pal. N.Y. Vol. ii, p. 137. 



Cladopora dichotoma ( n. s.). 



PLATE I. FIG. 5. 



CORAL ramose ; branches round, dichotomizing, ascending; 

 cell apertures in unworn specimens somewhat expanded and 

 broader below, in worn specimens round ; cells arranged in 

 alternating or somewhat quincunx order, distance from each 

 other greater than the diameter of the cell, sometimes more 

 closely arranged : surface smooth or granulate. 



This species bears a distant resemblance to some of the Niagara species of this 

 genus; but is much more robust, with the cells much larger and more distantly 

 arranged. 



Geological formation and locality. In calcareous rocks of the age of the 

 Hamilton group : New-Buffalo, Iowa ; Hamburg, Illinois. 



GENUS STRIATOPORA (HALL). 



" CORAL ramose, corolla solid ; stems composed of angular 

 cells ; apertures of cells opening upon the surface in expan- 

 ded angular cup-like depressions ; interior of the cell rayed 

 or striated ; striae extending beyond the aperture of the 

 cell". Pal. N.Y. Vol. ii, p. 156. " 



