274 PALEONTOLOGY OF ILLINOIS. 



surrounded by an irregularly radiating series of large canals; 

 between these are also a few apertures of vertical canals. Sides 

 of sponge with very irregular branching canal furrows. Minute 

 structure of skeleton like that of Zittelella and Anthaspidella. 



The character principally relied upon in distinguishing this 

 genus from Anthaspidella, is found in the very irregular dispo- 

 sition of the canals. The radiating canals are not, as in that 

 genus and Zittelella, arrayed in vertical series, but pass through 

 the sponge ma,ss in every direction, and the vertical furrows, so 

 characteristic of those genera, are therefore wanting. 



STREPTOSOLEN OBCONICUS U. & E. 



PL IV, fig. 4, 4a, 4b. 



Sponge obconical, gradually widening above the strong and 

 slightly expanded base. Upper surface flat or slightly depressed 

 with the margin rounded. The collection contains two speci- 

 mens of which the smaller one was figured. This has but one 

 osculum, sub-centrically situated, and around it a number of tor- 

 tuous interrupted and branching radiating canals. The larger 

 specimen has three oscula, each of which is surrounded by its 

 own irregular system of radiating canals. The average width 

 of the canals is about 1.2 mm. The sides of both specimens 

 present a very irregular system of tortuous branching canal 

 furrows. Near the base of the larger specimen there are evi- 

 dences of a dense dermal layer. The dimensions of this example 

 are as follows: height 75 mm.; greatest width about 60 mm.; 

 diameter of stem 17 mm. by 24 mm. 



None of the associated sponges resemble this species suffi- 

 ciently to necessitate detailed comparisons. The irregular in- 

 tertwining of the canals will distinguish it at a glance. 



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

 Trenton limestone, near Dixon, Illinois. 



CALATHIUM?? (?ZITTELELLA) INFELIX U. & E. 



PL V, flg. 1. la. 



Of this species only two imperfect examples have been observed, 

 but as they seem to be quite different from any of the associ- 



