246 • PALEONTOLOGY OF OHIO. 



vertical dissepiments represent two intersecting series of spicules, which 

 are more or l^ss completely amalgamated with one another. The minute . 

 crowded perforations, which pierce the concentric laminae and place the 

 interlaminar spaces in communication, may be regarded as representing 

 the inhalant apertures or " pores" of a sponge; whilst the large super- 

 ficial openings, and the large canals connected therewith, can hardly cor- 

 respond with anything else than the exhalant apertures or "oscula" 

 and the excurrent canals of an ordinary sponge. 



The Devonian rocks of Ohio, -like those of the same age in Canada, 

 yield a numoer of large and interesting forms of Stromatopora, of which 

 most appear to be new. They also yield examples of certain related 

 forms, which I shall describe as a new ge^us, or sub-genus, under the 

 name of Syringostroma. Lastly, I have found it necessary to establish 

 another genus, or sub-genus, which I have named Dictyostroma, for the re- 

 ception of an extra-limital form from the Niagara limestone, which I 

 have introduced here on account of its affinity to the preceding. 



Stromatopora ponderosa, Nicholson. 



Plate 24, flgs. 4, 46. 



Sarcodeme formin g a large sub-spherical mass, composed of numerous cal- 

 careous laminae disposed concentrically round an imaginary center, about 

 nine of them occupyi ng the space of one line. Interlaminar spaces crossed 

 by delicate vertical dissepiments, of which about five occupy the space of 

 one line. Surface undulated with numerous irregular rounded prom- 

 inences, which vary in height and in remoteness, but which have not 

 their summits perforated by any apertures. These prominences, as well 

 as the surface between them, are covered by small rounded tubercles, the 

 apices of which are in many instances clearly perforated by small circu- 

 lar openings. About six of these tubercles occupy the space of one line ; 

 they are about one hundredth of an inch in height, separated from one 

 another by about their own width, and they are always distinct and do 

 not coalesce or inosculate with one another. The surface also exhibits a 

 few large circular apertures, which are irregularly distributed in small 

 groups, and have a diameter of from one to two lines. These large apertures 

 have not elevated lips, but are flush with the general surface, and they 

 are the openings of large cylindrical canals which perforate the substance 

 of the mass. 



This remarkable species is nearly allied to S. tuherculata, Nich., from 

 which, however, it is distinguished by the following characters : 1. In- 



