BRYOZOA. 387 



SCALARIPORA Hall. Zoaria in every respect like those of Pris- 

 mopora, excepting that the faces of the triangular branches are 

 crossed by salient transverse ridges. 



Type: S. scalariformis Hall. Range, Upper Helderberg to 

 Hamilton. 



EVACTINOPORA Meek and Worthen. Zoaria free, consisting of 

 four or more vertical leaves, which radiate from an imaginary 

 axis so as to present in transverse section a star-shaped or 

 cruciform outline. Rays thin, double, celluliferous on both faces, 

 and free in the upper half; united, thick and non-poriferous in 

 the basal portion; thickest and most dense at the outer and 

 under edges. Zooecia with subcircular apertures. Interspaces 

 apparently solid at the surface, occupied by vesicular tissue in- 

 ternally. As growth proceeded, a gradually increasing deposit 

 of minutely perforated calcareous laminae covered the lower and 

 older portions of the zoarium. 



Type: E. radiata Meek and Worthen. Range, Burlington to 

 Keokuk group. 



GLYPTOPORA Ulrich, (Ceramella Hall.) Zoaria consisting of 

 thin bifoliate expansions, having both surfaces divided into 

 larger or smaller cup-shaped cavities, by the bifurcation and 

 coalescence of salient ridges; or of unilamellate bases, having 

 the coalescing ridges of the upper surface developed to such 

 a degree that they themselves form large expansions. The 

 ridges in both cases consist of two layers of cells growing in 

 opposite directions from a mesial lamina. The surfaces of 

 the ridges and the bottom of the cups exhibit rather regularly 

 distributed and more or less elongate solid maculae, which, as 

 thev are commonly depressed below the level of the surface, 

 have been called "dimples." Minute structure conforming with 

 that given for the family. 



Type: G. plumosa and G. keyserlingi Prout. Range, Bur- 

 lington to Chester. 



The following genera are placed here provisionally : 



GONIOCLADIA Ethridge, Jr. Carboniferous of Great Britain. 



CRISINELLA Hall. Lower Helderberg. 



THAMNOTRYPA Hall. Lower Helderberg. 



