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Cincinnati Society of Natural History. 



Evactinopora, Meek and Worthen. 1865. 

 (Proc. Acad. Nat. Sci. Philad. p. 165.)' 



Zoaria free, consisting of four or more vertical leaves, which radiate 

 from an imaginary vertical axis, so as to present in a transverse sec- 

 tion, a star-shaped, or cruciform outline. Rays thin, celluliferous 

 on both faces, and free above; united, thick and non-poriferous 

 below; thickest and most dense on the under and outer edges; 

 each divided in the middle by the thin, concentrically striated, 

 epithecse laminae, to which the lower ends of the tubes are 

 attached. Zocecia with sub-circular, oblique apertures, the lower mar- 

 gin being elevated. Interstitial spaces occupied by vesicular cells, 

 more or less densely filled by a laminar deposit of sclerenchyma. This 

 deposit is traversed by a vast number of minute, interrupted foramina 

 or canals, and, as growth proceeded was gradually drawn over the cell 

 apertures of the lower and older portions of the zoarium. 



Type : E. radiata, M. and W. Burlington and Keokuk groups. 



One of the most important and peculiar features of this genus is 

 found in the comparatively large, non-poriferous areas, less than half 

 of the zoarium of E. radiata being celluliferous. I have been for- 

 tunate in finding a number of excellent examples of this species, and 

 on Plate II. I have illustrated the characters not heretofore published. 

 The entire zoarium is elliptical in outline. The rays at a point about 

 one half their length from the rounded base, become free, are sharp- 

 edged, non-poriferous on each border, and gradually taper upward to a 

 point. These characters are shown in figs. 1 and la. The rays vary 

 in number from six to eight. Of twenty specimens found, four have 

 six; five, eight; and eleven, seven rays.* 



In the cellular structure, as is shown by figs. 16 and lc, the genus 

 is almost exactly like Coseinium, Keyserling, to which the genus is 

 therefore closely allied. But the great and very obvious differences in 

 growth, make comparisons between the two genera quite unnecessary. 



FISTULIPORID^. 



This family differs from all other groups of Palaeozoic Bryozoa, ex- 

 cepting the Cystodictyonidce, in the possession of a vesicular intersti- 



* Meek and Worthen, the authors of the species, credit it with eight rays, and regard 

 another specimen with only six rays, as belonging to another species, which they name 

 sexradiata. Singularly enough, their figure of the latter shows only five rays. Under the 

 circumstances 1 must believe that this discrepancy is due to the artist, and if E . sexradiata 

 differs in no other respect from E. radiata, then the name should be abandoned. 



