192 . Palcemanon cratera. 



of the sponge. It is also observaUe from a cross section tlmt long slits, 

 l)ranching outwardly, and becoming by degrees smaller and more 

 obscure, radiate from the axis toward the circumference of the sponge, 

 running through the larger openings. In this species, too, as in the 

 A. prcemorsa and A. stellatim sulcata, the inner texture of the sponge is 

 composed of numerous small bodies, hanging together in the shape of 

 stars. We can distinguish these very plainly on the outer circum- 

 ference, which forms the lower end of the specimen, by the fractured 

 edges of the surfaces, in that part where the substance of petrifaction is 

 transparent, blue-gray chalcedony. These stars, however, seem to be 

 more irregular than ui the other two species, and generally to be four- 

 rayed instead of six. Without this concurrence of its inner structure 

 it might be doubtful to what genus to ascribe it, as from the want of 

 the lower end of the simple specimen, that I have before me, and from 

 the cylindrical form of the body, it could hardly be determined. 



Its almost cylindrical or rolling form and ring-like prominences 

 make this species somewhat resemble the Scyphla-articulata (Goldfuss), 

 and also the Seijphia-cijlindrica (Goldfuss), var. rugosa of Streitberg, 

 However, the Jura species are wanting in the inner perpendicular pipes 

 belonging to our species, and Scyphia-articulata is, moreover, dis- 

 tinguished by a beautiful cross-barred surface. 



Palwmanon cratera — (Rcemer) . 



A sponge, bowl or goblet-shaped, w^ith its whole surface covered 

 with dispersed larger openings, having between them smaller openings, 

 like tlie points of needles. The larger openings are much more distinct 

 and better defined upon the upper depressed surface than upon the 

 side surfaces, upon which they are often wholly unrecognizable. 

 Irregular furrows or streaks are drawn from the hollow of the edge 

 that circumscribes the upper side running over the outer side. The 

 lower end is formed by a horizontal plane, truncated surface, similar 

 to that of the A-dylospongia prcemorsa. Sometimes, but more seldom, 

 it is rounded off. At times, too, the upper surface is much less 

 depressed. In those cases forms are presented which are similar to the 

 Astylospongia prcemorsa, and it seems to me not at all impossible that at 

 one time complete transformations between the twH) species occurred. 



