SPONGES. 265 



ANTHASPIDELLA OBLIQUA U. & E. 



PL IY, flg. l.la. 



Sponge funnel-shaped, gradually expanding above the sub- 

 cylindrical stem. Margin of cup narrowly rounded and some- 

 what oblique. Upper surface depressed, and sloping gradually 

 towards the centre, where the best specimen shows a group of 

 three oscula, each surrounded by from twelve to sixteen radi- 

 ating canals, which inosculate with each other and bifurcate 

 rather freely toward the outer margin of the sponge. The 

 sponge tissue between the canals is thinner than usual, being 

 generally of less width than the diameter of the canals. Outer 

 and under surface apparently smooth or even, with the sides 

 concave and traversed by vertical furrows in which the closely 

 arranged apertures of the radiating canals, which have pene- 

 trated the walls of the sponge from the upper surface, are 

 plainly to be seen. On portions of the stem the canals are very 

 irregular. 



Only two imperfect specimens of this species have been observed 

 but as they show decided peculiarities, it has been thought 

 desirable to describe them. Judging from the form of the speci- 

 mens, the affinities of the species lie with A. fenestrata, from 

 which, however, it is easily distinguished by the smaller size, 

 more expanded cup, and different arrangement of the canals 

 and oscula on the upper surface. 



Diameter of cup of best specimen 40 mm.; entire height 53 

 mm.; diameter of stem about 15 mm.; depth of cup 9 mm. 



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

 Trenton limestone, near Dixon, Illinois. 



ANTHASPIDELLA? MAGNIFICA U. & E. 



PL VIII, fig. 2, 2a, 2b. 2c. 



Of this fine species the collection affords but a single example, 

 which is figured, partly in outline, on plate VIII. By sawing it 

 vertically through the centre we were enabled to free the deep 

 cup of the enclosed rock, and to trace out the canal systems 

 which are well shown in the wall sections, The entire specimen 

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