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Cincinnati Society of Natural History. 



Ehombopora, Meek, 1871. 



(Pal. Eastern Nebr aska.) 



Zoaria ramose, branches slender. Zooecia tubular, radiating in all 

 directions from an imaginary axis. Walls abruptly thickened in the 

 "matured" region, where the diameter of the visceral cavity is also 

 more or less constricted. Zooecial apertures circular or oval, placed 

 at the bottom of more or less obviously impressed, sloping, rhom- 

 boidal to hexagonal "vestibules." Ridges separating vestibules 

 spiniferous. Spines hollow, often of two kinds, large and small, the 

 latter most numerous, and surrounding the apertures in a single or 

 double series, while the larger spines are usually developed only at the 

 upper extremity of the cell. Diaphragms generally absent, always 

 few. Zooecial apertures frequently closed by centrally perforated 

 opercula. 



Type: B. lepidode?idroidea, Meek. Upper Coal Measures. 



Several species of this genus show more or less clearly that the 

 inner layers of the cell walls are perforated by a large number of minute 

 foramina or canals, which appear to have communicated with the hollow 

 vertical spines. I have also noticed them in a transverse section of 

 Rhabdomeson gracile (Fig. 8, PI. I.), and it is possible that such 

 foramina are characteristic of the family. 



Through B. crassa, n. sp., and Ceripora interporosa. Phill., which, 

 if my specimens have been correctly identified,* must be referred to 

 this genus, we can trace a resemblance to carboniferous species of 

 Batostomella (e. g. B. tumida, Phill., sp.). In both of those species 

 the hollow spines are represented in the weathered condition of the 

 zoarium by an equal number of minute pits. This peculiarity can 

 not be explained satisfactory, except by supposing that these 

 structures in the two species under consideration possessed a larger 

 cavity than was usual, which, as growth proceeded, was filled by a 

 secondary deposit. In tangential sections they present nothing differ- 

 ent from the usual appearance of spiniform tubuli. In all other respects 

 the two species agree closely with typical species of B/iombopora, and 

 consequently differ from species of Batostomella. 



My observations show that in the Palaeozoic rocks of America the 

 genus is represented as follows: in the Niagara group by at least 



*My specimens were received from Mr. G. R. Viae, who, in his last report to the British 

 Association on Fossil Polyzoa, places the species with Heteropora. I must differ with him 

 on this point, as I can not find that the species in question is more than only remotely 

 related to species of Heteropora. 



