250 PALEONTOLOGY OF OHIO. 



The specimen from which the above description is taken is imperfect, 

 but forms a nearly plain mass, about half a foot in length by four inches 

 in width, and about one inch and a half in thickness. The speci- 

 men does not, however, exhibit the margins, the true surface, or the 

 under side, and the entire mass must, therefore, have been of very large 

 size. 



The density of the vesicular tissue of this species is so great, and the 

 cellular compartments are so reduced in size, that it may, perhaps, be 

 properly regarded as belonging to the genus, or sub-genus, Syringostroma, 

 rather than to Stromatopora proper. I can not, however, discover that 

 the mass is permeated by any system of canals running parallel with the 

 surface, and I have, therefore, retained it in the meanwhile in Stromato- 

 pora. 



In some respects S. nodulata resembles certain of the forms included 

 by Goldfuss under the name of Stromatopora polymorpha; but the descrip- 

 tion of the internal structure of this species is too insufficient to allow 

 of any comparison, whilst Goldfuss has clearly included more than one 

 form under this head. The present species, also, is distinguished hj ex- 

 hibiting no perforations at the summit of the nipple-shaped superficial 

 prominences, by the fact that the eminences in question are perfectly 

 regular in size and arrangement, and by the great dimensions of the 

 • entire mass. 



The characters which distinguish S. nodulata, when taken in combina- 

 tion, may be summed up as follows : 1. The laminse and vertical rods 

 ^ are so thickened as to reduce the size of the cellular compartments of the 

 organism to a great extent, and the cells are generally placed one above 

 the other in more or less regular vertical lines. 2. The cells of each suc- 

 cessive layer open into those of contiguous strata by means of closely 

 approximated rounded or sinuous perforations, the cells of the uppermost 

 layer doubtless communicating in a similar fashion with the exterior 

 medium. 3. The surface is not tuberculated or granulated, but is smooth, 

 and is covered with numerous large rounded or nipple-shaped elevations, 

 which are very uniform in size and height, and are disposed in diagonal 

 lines placed at small intervals apart. 4. The eminences just mentioned 

 . are not perforated by any openings other than the minute ones which 

 closely cover the entire surface; and there have, therefore, been hitherto 

 detected no traces of " oscula " or exhalant apertures. At the same time, 

 such apertures doubtless existed, and will be found in more perfect ex- 

 amples. 5. Surfaces covered with the nipple-shaped eminences above 

 spoken of occur at various levels throughout the mass, which would 

 thus appear to have increased in size by the periodic formation of con- 



