AMORPHOZOA FROM THE SILURIAN AND DEVONIAN. 249 



tions, about one-fourth of a line in diameter, passing nearly at right 

 angles through the numerous layers composing the mass, at intervals 

 varying from one to two lines apart." 



From the other recorded spefcies of Stromatopora the present species is 

 readily distinguished by its massive and rounded form, its smooth sur- 

 face, remote oscula, and the characters of the lamination. 



Position and locality : Corniferous limestone, Marblehead, Ottawa county, Ohio. 



Stromatopora nodulata, Nicholson. 



Plate 24, figs. 3, 36. 



Sarcodeme forming an irregular mass, the precise form and dimensions 

 of which are unknown, though it evidently attained a great size. The 

 mass is composed of concentric laminae of great thickness, from four to 

 six occupying the space of one line. The interlaminar spaces are pro- 

 portionately reduced in height, and are crossed by calcareous pillars, 

 which give rise to a number of little oval or circular compartments, 

 about six of which occupy the space of one line. Both the horizontal 

 laminae and the vertical pillars are, however, so thick that the cellular 

 compartments produced b}'' their intersection are reduced to minute 

 rounded cells of unequal sizes in successive layers. The compartments 

 or cells are usually placed successively, one above another, in vertical 

 rows, giving the section of the fossil a very characteristic appearance. 

 The surface of the mass (which does not seem to be the true surface) is 

 covered with large and close-set, regularly disposed, nipple-shaped or 

 • conical eminences, which are arranged in diagonal lines, each having a 

 height of two lines, and a diameter at the base of about five lines, and 

 being placed about one line apart at their bases. Similar mammillated 

 surfaces occur throughout the mass at different levels. These large and 

 regular rounded elevations show no sign of being perforated at t^ir 

 summits by any apertures of sufficiently large size to be considered as 

 "oscula," nor are any traces of such to be detected elsewhere. The 

 entire surface, however, both generally and of the mammillations, is 

 covered with very minute rounded or elongated perforations, which have 

 often a sinuous or vermicular form, and appear to lead into the successive 

 interlaminar cells. These minute pores are not only extremely small, 

 but are excessively crowded, and on the elevations above spoken of they 

 are arranged more or less in lines radiating from the summit. Except 

 for these perforations, the surface is smooth, and there are no tubercles 

 or granules. 



