AMOEPHOZOA FROM THE SILURIAN ANB DEVONIAN. 253 



Syeingostroma columnaeis, JSTichOlson. 



Plate 24, figs. 1, la. 



Sarcodeme forming a sub- spherical (?) mass of large size, composed of 

 extraordinarily delicate calcareous concentric laminee (apparently about 

 twenty in the space of one line), separated by vertical dissepiments. 

 The entire mass is traversed by a series of vertical columns, about half 

 a line in diameter, and placed at distances apart of from one-half to two- 

 thirds of a line, the upper ends of which protrude above the upper sur- 

 face as a series of small, close-set, rounded elevations or tubercles. Each 

 of these vertical columns is formed by an upward curvature of the con- 

 centric laminffi of the mass, and is quite solid, the cells and vertical dis- ■ 

 sepiments being wanting here, and the successive concentric laminae 

 being in actual contact. On the other hand, in the spaces between the 

 columns the concentric laminae are curved downward, and are separated 

 by interspaces crossed by vertical dissepiments- There is thus produced 

 a system of cells similar to those of Stromatopora proper, the dissepi- 

 ments, however, being extremely thick, and the cells extraordinarily 

 minute. Besides the true cells, the intercolumnar spaces show larger 

 circular openings, which usually have a diameter of from one-fourth to 

 one-third of a line, and are the apertures of a series of canals running 

 parallel with the surface. These horizontal canals are irregularly dis- 

 posed, though often placed in vertical rows, and they are fewer in num- 

 ber than in the preceding species. 



The surface is covered with numerous low, rounded elevations, nearly 

 one line in diameter, and placed about half a line apart. The central 

 portion of these elevations is formed by the projection above the surface 

 of the vertical columns before noticed, and round this central area, in 

 the best preserved portions of the surface, is seen a row of minute 

 rounded apertures, which have a diameter of about one- sixth of a line, 

 and are doubtless the openings of a series of vertical canals. There are 

 indications that the surface between the tubercles is perforated with still 

 more minute openings, corresponding with the cellular compartments of 

 the mass, but I have not been able to determine this in a satisfactory 

 manner. 



The specimen described is a fragment about six inches long and eight 

 lines in thickness, apparently derived from the exterior of a large mass. 



The species can not possibly be confounded with any other, as its 

 characters are entirely unique. 



Positicm and locality : Cornif erous limestone, Sandusky, Ohio. 



