American Palceozoic Bryozoa. 



139 



the former, and none, so far as I have been able to determine, in the 

 latter; *ind (2), the thickness of the cell-walls is more variable in 

 those species of Spatiopora than in Palceschara. In the second 

 feature, Spatiopora probably resembles more nearly such species 

 of Ceramopora, as C. whitei, James. On the other hand, Palceschara 

 strongly resembles certain species of Jlembranipora, and I am inclined 

 to regard the genus as a member of the Membraniporidce. Through 

 the channel thus indicated (if the step between the species of Spatio- 

 pora and Palceschara be not considered too great), a relationship is 

 established between the Cheilostomatous Br}'ozoa and the Monticuli- 

 poridce. Myriozoi/m, Donatio a genus of the Cheilostoma, like some 

 of the Ceramoporidce and Fistuliporidai, has the interstitial cells 

 closed by a calcareous membrane, and has the true tubes provided 

 with two lamella?, which are placed near together, and remind one 

 strongly of Crepipora and Didymopora, Ulrich. 



Stellipora, Hall, and the nearly allied form tor which Dana proposed 

 the name Constellaria, show many points of resemblance to several 

 genera of the Cyclostomata; and, in fact, Jules Haime, in his Mono- 

 graph of the Jurassic Bryozoa, regarded such undoubted Biyozoans as 

 the species collected together by D'Orbigny, under the name of Radi- 

 pora, to be congeneric with species of Constellaria, and he conse- 

 quently placed Radipora as a s\ r nonym under Dana's genus. Though 

 I am not prepared to follow that authority in his disposition of Radi- 

 pora, I admit that the resemblance between the Silurian and Mesozok- 

 forms is very strongly marked. I can scarcely believe that any one 

 will question the relationship between Stellipora (and Constellaria) 

 on the one side to the Monticuliporidce, and on the other to the Fistu- 

 liporidai; and also that the genus has certain characters which sepa- 

 rate it from all other genera of those families. The most important 

 of these characters is found in the arrangement of the cells. In the 

 center of the "maculae" is a depressed space from which proceed in 

 all directions a greater or less number of slender rays. Both the rays 

 and the central space are occupied solely by interstitial cells. Between 

 the rays the surface is raised, and each of the elevated rays is occupied 

 b} r the apertures of eight or more true cells. Lichenopora, Buskia, 

 and Radipora, have similar stellate protuberances, and with the 

 exception that in those genera diaphragms are only sparingly devel- 

 oped, I can find no characters of more than generic value to separate 

 them from Stellipora. 



The family Stictoporiduz, through several of its members, approx 



