SPONGES. 267 



This species differs considerably in its canal system from A. 

 florifera and A. mammulata. In those species the vertical 

 canals are almost entirely restricted to the oscula, while the 

 radiating canals are much the more numerously met with in 

 sections. The opposite is the case with A. magnifica, since the 

 radiating canals are but rarely seen in the sections, while the 

 vertical ones are numerous. None of the other species seem to 

 have been provided with an outer layer like that described 

 above, as in all, (so far as their preservation will admit of de- 

 termining this point) the radiating canals open on the outer 

 surface into the vertical grooves. Except at or near the margin 

 of the cup, this is not the case in A. magnifies,, since in this 

 species they do not pass through the outer layer. The func- 

 tions of the latter was probably the same as that of the ordi- 

 nary dermal layer of the sponges. The differences may indicate 

 another genus of this peculiar family of sponges, but till they 

 are proven to be of generic importance by finding them in other 

 forms, we prefer to place the species, at least provisionally, with 

 AnthaspideHB. 



Position and locality: Twenty-five feet above the base of the 

 Trenton limestone, near Dixon, Illinois. 



ZlTTELELLA nOV. gen. 



Sponges simple, pedunculate and attached, varying in shape 

 from depressed obconical, turbinate or sub-spherical, to sub- 

 cylindrical : rarely lobate. Upper surface with a shallow central 

 depression into which a variable number of thin-walled vertical 

 tubes, extending through to the base of the sponge, open. 

 Canal system consisting principally of a series of radiating 

 canals, which may inosculate freely with each other, or only to 

 a limited degree in their passage through the walls of the sponge 

 from the outer surface to the vertical central tubes. The radi- 

 ating canals are closely arranged in vertical series, separated 

 by spicular tissue from one to three times as wide as the canals. 

 This arrangement of the canals gives the sponge the appear- 

 ance of being divided by vertical fissures. Interior skeleton as 



