266 PALAEONTOLOGY OF ILLINOIS. 



is funnel or goblet-shaped, the stem strong, sub-cylindrical, 

 irregularly expanded below, and marked by the more or less 

 confluent and irregularly distributed apertures of small canals, 

 rarely more than 0.5 mm. in diameter. Above the stem on the 

 outer side of the cup, the same irregularity pertains to the dis- 

 tribution of the canal openings and continues to within one 

 inch of the cup margin, where they arrange themselves into 

 vertical series. The outer surface of the cup, especially just 

 above the stem, is faintly mammulated, the broad eminences 

 low and with an obscure vertical arrangement. The cup is deep, 

 and on its sloping sides presents a large number of small 

 slightly raised stellate oscula, 1.5 to 2 mm. in diameter; ten 

 or more may be counted in a space one inch square. Below the 

 dense cortical substance which covers the intermediate spaces 

 in the perfect state, the canal furrows inosculate freely, but a 

 tendency to follow lines radiating from the centre of the cup to 

 the margin is always maintained. A vertical section of the 

 specimen shows that the central portion of the stem is traversed 

 by vertical canals opening into the base of the cup. The same 

 series of canals continues on into the walls of the cup. Here 

 they originate along an imaginary line dividing the sponge wall 

 into two layers, an inner one that nearly maintains its thick- 

 ness throughout the cup-wall, and a thinner outer layer that 

 gradually diminishes in thickness from the base of the stem to 

 the margin where it is wanting. The canals in question pass 

 through the inner layer in a curved direction and open at right 

 angles with the surface into the cup cavity. The outer layer is 

 traversed in an opposite direction by similar, but shorter and 

 more numerous canals. A third series is shown in the upper 

 portion of the section figured (PI. VIII, fig. 2c). These proceed 

 apparently from the oscula, and passing through the inner 

 layer in an opposite direction from those already described, ter- 

 minate, at the line marking the beginning of the outer layer. 

 The spicular structure does not differ, so far as observed, from 

 that of A. florifera and the other species. 



Height of specimen 150 mm.; diameter of stem 35 mm.; ap- 

 proximate diameter at cup margin 140 mm.; depth of cup 70 

 inni.; average thickness t)f cup wall 17 mm,; thickness of inner 

 layer about 10 ram, 



