PALAEONTOLOGY OF IOWA. 653 



Ptylopora prouti ( n. s.). 



PLATE XXII. FIG. 6 a, b, c, and FIG. 7. 



MIDRIB strong, rounded on the celluliferous side, subangular 

 on the poriferous side, and marked by a double row of cel- 

 lules, often giving a carinate appearance to the central part, 

 which is margined by two narrow grooves containing the 

 oval cellules. Branches, on the noncelluliferous side, rounded 

 and striated ; on the celluliferous side, carinate in the middle, 

 and the cellules placed in a depression on each side, with 

 the narrow outer margin slightly elevated. 



Fig. 6 a. Celluliferous side of a specimen, natural size. 



Fig. 6 b. The same enlarged. 



Fig. 6 c. A portion still farther enlarged. 



Fig. 7. Exterior of the same species. 



Geological formation and locality. In the Warsaw limestone : Warsaw, 

 Illinois 



Among the Bryozoa in this rock, I have noticed, in addition to those described 

 above, several other genera, among which are CLATHROPORA [ = CosciNUM?], STIO 

 TOPORA and CALLOPORA, which are likewise Silurian genera. Among the latter, I 

 have designated the following : 



Callopora punctata ( n. s.). 



FROND branching, dendroid, round or oval in section ; in- 

 ternal structure radiatingly fibrous. Surface transversely 

 ridged or nodose : cells round or somewhat pentapetalous, 

 small, uniformly distributed over the surface ; intermediate 

 spaces minutely celluliferous : the surface punctate ; three, 

 four, or more rows of punctse between the cells. 



Geological position and localities. In the Warsaw limestone : Keokuk, 

 Iowa ; Warsaw, Illinois. 



