128 



Cincinnati Society of Natural History. 



The question, what is the true purpose of these remarkable structures, 

 is indeed a most difficult one. That they should, in all eases, be 

 merely appendages to the zoarium, and not possess some really import- 

 ant relation to the other parts of the zoarium, is scarcely probable; 

 and I can hardly doubt that their purpose was, if not identical with, 

 at least similar to, that of the small sockets which serve as a founda- 

 tion for the vibracula of many of the recent Bryozoa. This suggestion 

 is meant to apply only to the large and comparatively remote " spini- 

 form tubuli" of Dekayia, E. and H., Heterotrypa, Nich., and a few 

 others. I doubt considerably whether these are of the same nature as 

 the smaller and much more numerous ones, characterizing the genera 

 Stenopora, Lonsd., Batostomella, Ulrich, Amplexopora, Ulrich, Atac- 

 topora, Ulrich, and Bhombopora, Meek. A different and quite plaus- 

 ible explanation, I believe, can be given for the latter. We find, 

 namely, among the Cheilostomata, many forms having a row of short 

 and stout, chitonous or calcareous bristles, placed upon the walls of the - 

 cell-apertures, which after the death of the zooid fall off, leaving 

 minute pits in the summits of small blunt spines. That in the Monti- 

 culiporidce these hollow spines are drawn out into tubuli, I believe, is 

 due simply to the fact that as growth proceeded, each successive layer 

 of cells (i.e., each portion of the tubes between succeeding diaphragms), 

 was placed in all respects directly over the preceding layer, and in con- 

 sequence the growth of the " spiniform tubuli," was carried on simul- 

 taneously with the formation of the walls of the new layer of cells. 



VI. Wall- Inflections. — True " septa" do not occur in any species of 

 the MonticuUporidw, nor Fistuliporidas; nor even anything of the nature 

 uf the " spiniform septa" of the Favositidce. I believe that I can 

 safely assert, that in the forms under consideration, where septate or 

 irregularly indented cells are present, with the exception of Didymo- 

 pora, they are always due to the development of " spiniform tubuli" in 

 the spaces between the angles of the tubes. The floriform cell is most 

 distinct in Amplexopora septosa, Ulrich, and in the species of Atacto- 

 pora, in which forms, on cursory inspection, the inflections might be 

 regarded as of the nature of septa. In other species, notably Batos- 

 toma implicata, Ulrich, these inflections are not nearly so abrupt, 

 but the cell walls are simply bent inward, in two, three, or four 

 places, according to the number of "spiniform tubuli" having an 

 effect upon the contour of the cells. In Didymopora, a new genus 

 of the Fistuliporidw, yve find either two inflections as in Batos- 

 toma, or two tluu and converging lamellae, which are placed on one side 



