PLATE VII. 



PAGE. 



Fig. 1. CAMAKOCI/ADIA DICHOTOMA U. & E 281 



1. A group of sterns of the ordinary appearance and size. 



1 a. Vertical section of a specimen preserving the walls, x9. The walls are 



changed to crystalline calcite, and show no structure. 



1 b. Transverse section of another example, x9, showing minute three- 

 rayed spicules in the chambers. 



Figs. 2, 2 a and 2 b. An undetermined fossil from the Dixon sponge layer. Possibly 

 a Stromatoporoid. Not described. The specimens are in the Illinois 

 State Museum. 



Fig. 3. ACTINOSTROMA? TKENTONENSE U. & E 282 



3. View of the lower side of a specimen. Natural size. 



3 a and 3 b. Vertical and transverse sections, x!8, showing a close agreement 



in minute structure with the Anthaspidellidce. Trenton limestone, 

 Dixon, 111. Illinois State Musoum. 



Fie. \. SYRINGELASMA WOKTHENI Ulrich* 250 



4. View of the only fragment seen. Natural size. Both sides of the speci- 



men aie practically alike. 



4 a. Enlargement of 4 c, being a section through the center of the expan- 



sion, and parallel with the surface, x!8. 



4 '. Transverse section, x!8, showing the irregular spicular mesh. 

 4 d. The fractured edge of fig. 4, showing thickness of same, the vertical 



canals, and the horizontal channels. Natural size. 



4 e. Vertical section, natural size, showine direction of minu'e canals. 



Hamilton group, Thunder Bay, Mich. 

 Prof. A. H. Worthen's collection. 



Fig. 5. ACTIXOSTKOMA, sp. undet 221 



5. The polished edge of a specimen, natural size. 



5 a. Transverse section of same, x!8. showing the radial pillars. 



5 b. Vertical section of same, showing the radial pillars and the horizontal 

 arrangement of the rays. These figures are introduced for comparison 

 with the Anthaspidellidce. 



'Just after the text for the sponges had gone through the press, it was noticed that 

 Syringophyllum had been preoccupied by Edwards and Haime, for a genus of corals. 

 Syrinyelasma is proposed instead. 



