258 PALEONTOLOGY OF ILLINOIS. 



ANTHASPIDELLA MAMMULATA U. & E. 



PI. I, Pig. 1, la, Ib, Ic, Id. 



Sponge having the shape of a widely expanded funnel, with 

 the margin abruptly rounded. Upper surface deeply concave. 

 Oscula numerous, occurring at intervals varying from 5 to 

 20 mm. They occupy the summits of more or less elevated 

 monticules, and when the compact dermal layer is preserved, 

 their abruptly depressed apertures, having a diameter of 2.5 mm. 

 or less, are rounded and sharply margined. When the outer 

 layer is wanting, they are surrounded by from six to ten radiat- 

 ing canals. As usual, the oscula are most numerous in the 

 central portion. The furrows of the radiating canals inosculate 

 rather freely. Under surface comparatively even, with the sides 

 nearly straight or faintly convex, and marked by radiating 

 furrows, of which seven to nine occur in 0.5 of an inch. The 

 margins of these furrows may be entire, more often serrated, and, 

 less commonly, connected with those adjoining by transverse 

 canals. 



The canal system, as brought out by sections, consists princi- 

 pally of the radiating canals, which, penetrating the sponge 

 wall in a curved direction and a;t right angles to the minute 

 canals formed by the spicular mesh, are arranged in vertically 

 superimposed series. Those of adjoining series are connected 

 with each other at more or less frequent intervals by short 

 canals, arranged in such a manner that they might be mistaken 

 for another series of canals running parallel with the capillary 

 canals. This, however, is not their true nature, as the section 

 clearly shows that each of the supposed canals is formed by a 

 series of closely approximated connecting canals. (See PI. I. 

 fig. Ib.) 



Diameter of an ordinary sized example, 100 mm.; entire height 

 about 38 mm.; depth of cup, 25 mm.; thickness of wall from 7 

 to 10 mm. 



The greater concavity or depth of the upper surface and 

 general form of the sponge, separate A. mammulata from such 



