354 PALAEONTOLOGY OF ILLINOIS. 



When I think of the hundreds of exquisitely preserved examples 

 of species of the genera in question that I have seen and 

 studied, it seems almost ridiculous that argument is necessary 

 to show them to be a structural unity and not composed of 

 two separate and distinct organisms. It seems to me that Mr. 

 Shrubsole must be lacking sadly in caution, as well as in respect 

 for the work of others, or he would not express himself so 

 dogmatically as in the above samples upon a question that 

 manifestly he can scarcely have touched. Both Mr. Shrubsole 

 and Mr. Vine could easily have verified the structural unity of 

 the Fenestella interior and the supposed parasitic coral by mak- 

 ing a few judicious thin sections of specimens preserved in lime- 

 stone, those in shale being usually so much compressed that the 

 union between the two fenestrated expansions is broken. Had 

 they had an opportunity of examining some of the silicified spec- 

 imens from the Falls of the Ohio river, which show the delicate 

 net-work perfectly free from the matrix, I am sure their present 

 views upon Hemitrypa and Unitrypa would never have been 

 published. Still, as the outer structure of Hemitrypa, etc., is 

 by many regarded as of the nature of a parasite, some refuta- 

 tion is required. I will therefore ask a few questions. 



If the structure is viewed as a parasitic bryozoan similar to 

 Paleschara Hall, or to Monticuliporoids of the type of Lepto 

 trypa, upon what grounds is the supposition based? The 

 zooecium of a bryozoan raust before all things have a bottom 

 or basal plate. Is this present on the inner side of the external 

 net-work? I answer emphatically, no. On the contrary the 

 little openings communicate without any interruption with the 

 interior space between the two expansions. It is true, of course, 

 that over the basal portion of old examples of Hemitrypa and 

 Unitrypa, the fenestrules on both surfaces of the zoarium are 

 covered by a thin calcareous membrane, but this fact has no 

 bearing whatever upon the question. Again, if the suspected 

 expansion is of the nature of Leptotrypa, why do we not find 

 clusters of large cells, which are invariably present in such 

 forms? And why do the little openings in the superficial net- 

 work of Hemitrypa correspond so exactly both in position and 

 number with the zocecial apertures beneath them in the cellu- 

 liferous expansion? Surely this is not simply a coincidence. 



