298 PALEONTOLOGY OF ILLINOIS. 



ous margin, which is so characteristic a feature of the zoarium 

 of that family as well as of the PTILODICTYONID^ and CYSTO- 

 DICTYONIDJE, is essentially the same thing, since its minute structure 

 is precisely similar to that of the maculae. The non-poriferous 

 margin further agrees with the "maculae" in the fact that the 

 zocecia which are nearest to the margin are almost invariably 

 larger than those occupying the central region of the stipe. In 

 Prismopora serrata Meek, and P. trifolia Rominger, the mor- 

 phological identity of the non-poriferous margin and the "mac- 

 ulae" is clearly shown, the two being confluent. 



As regards the uses of the "monticules" and "maculae," the 

 only suggestion that seems at all applicable, is that they had 

 something to do with the reproductive functions. The large 

 cells which occupy the monticules or surround the maculae must 

 in that case have been the receptacles in which the embryo were 

 developed into the larval stage. This explanation is made very 

 plausible by a comparison with the goncecium of Crisia, which 

 is nothing more than a slightly modified zooecium set apart 

 for reproductive functions. The ocecium of many other Cyclo- 

 stomatous Bryozoa is simply an inflated Zooecium, which also 

 may be slightly modified in other respects. In Strotopora, a 

 new genus of the FISTULIPORID^E, the surface exhibits more or 

 less numerous cells which are curiously modified in having the 

 apertures abruptly expanded to two or three times the normal 

 width. In the perfect state the aperture is arched over and 

 presents the appearance of a small vesicle. That these struc- 

 tures represent ooecia will scarcely admit of doubt. 



III. Mesopores and vesicular tissue. The term "Mesopores" 

 was proposed by Nicholson and Foord for the cells which oc- 

 cupy the spaces between the true Zooecia previously known as 

 interstitial cells and cancelli.* They applied the term equally 

 to the interstitial tubes of CaUopora, Prasopora, Diplotrypa, 

 Eeterotrypa, etc., and to the vesicular cells of Fistulipora. These 

 structures are, however, very distinct and ought to be known 

 by different names. I propose, therefore, that the use of the 

 term "mesopores" be restricted to the tubular interstitial cells, 



* Prof. Busk and other authors applied the name "cancelli" to the interstitial tubes 

 ol Heteropora and other Bryozoa of that type. Mesopores is supposed to be a more 

 appropriate term, and is used by me in its stead. 



