268 PALEONTOLOGY OF ILLINOIS. 



in Anthaspidella, excepting that the capillary canals run parallel 

 with the sides of the sponge wall, and open only at the upper 

 surface. 



Under surface sometimes covered with a dense dermal layer. 

 Type Z. typicalis* 



ZlTTELELLA TYPICALIS U. & E. 

 PL V, fig. 5, 5a. 



Sponge vase or funnel-shaped, with a comparatively long sub- 

 cylindrical stem. Upper surface slightly depressed, and marked 

 by somewhat regular radiating canals uniting more or less freely 

 with each other by means of lateral divisions, or by inoscula- 

 tion. The width of the channels is about 0.6 mm., while from 

 eight to ten occur in 10 mm. The depressed centre of the cup 

 surface exhibits the apertures of nearly fifty vertical tubes, each 

 about 0.8 mm. in diameter, having very thin walls. The sides 

 of the sponge spread rapidly above the stem, and usually ex- 

 hibit a number of shallow vertical depressions, as well as the 

 vertical channels. About five of the latter occur in a space 10 

 mm. wide. The vertically arranged mouths of the radiating 

 canals are shown in the place of the channels when the speci- 

 mens are worn; six or seven in a series 10 mm. long. On the 

 stem the channels are short, numerous, and irregularly arranged. 

 From the fact that the radiating channels of the upper surface 

 are more numerous than those on the sides, it appears that 

 many of the radiating canals are blind, (L e. terminate before 

 reaching the outer surface) or, that all of the radiating channels 

 are not converted into internal canals. 



The best specimen (a small one) is 44 mm. in height, and 60 

 mm. in diameter; the stem about 18 mm. long, and 20 mm. in 

 diameter. 



The above describes the typical form of the species, but the 

 collection contains a number of sponges from the same locality, 

 which, while they do not appear to be distinguishable by specific 



* The absence of radiate oscula distinguishes this genus from Anthaspidella. 

 Aulocopium and Climacospongia, have different canal systems. 



