108 



OHIO FOSSILS 



Key to the Commoner Pennsylvania!! Bryozoa of Ohio 

 (see p. 4 for use of keys) 



2. 



3. 



6. 



8. 



a) Colonies twig-like, branching 2 



b) Colonies leaf-like 6 



a) Branches almost cylindrical 3 



b) Branches flattened 5 



a) Branches longitudinally ridged Pinnatopora 



b) Branches not longitudinally ridged 4 



a) Branches about l/8 inch in diameter Rhombopora 



b) Branches about l/4 inch in diameter Tabulipora 



a) Branches with wavy edges Prismopora 



b) Branches with straight edges Cystodictya 



a) Parasitic in the shell of brachiopods and pelecypods; 



branching irregularly, with sac-like appendages 



attached to the branches Bascomella 



b) Branching regularly, colony made up of rods joined 



together by cross-bars 7 



a) Cross-bars curved or angulated Septopora 



b) Cross-bars straight 8 



a) Rods with wavy ridges between the rows of cells Polypora 



b) Rods without such wavy ridges Fenestrellina 



Pinnatopora colonies look like miniature fir twigs. The branches 

 are nearly cylindrical, they fork many times, and are ribbed longi- 

 tudinally. The tiny cups alternate in two rows between the ribs on the 

 branches. P. whitii (fig. 287) is common in some beds. 



Fig. 287 1&W"° 



Rhombopora is also twig-like but the branches fork very little; 

 fragments more than 1 inch long show no signs of forking. The branches are very 

 slender, about l/8 inch in diameter and about half the size of the branches of Tabul- 

 The cells are small, about 20 rows of them around the branches. 



lpora . 



lepidodendroides (fig. 288) is common in some beds. 



R. 



Tabulipora is like Rhombopora but the branches are twice as thick, about 1/4 

 inch in diameter. The branches also fork more frequently in Tabu l- 

 ipor a. T. ohioensis is common in places. 



Fig. 288 - 



Two genera of twig-like bryozoans with flattened branches are easily 

 recognized. In Prismopora the branches have wavy edges and a strong ridge 

 runs down the middle of the branch. P. sereata (fig. 289) is the common 

 species. 



Cystodictya lacks the median ridge of Prismopora and the flattened 

 branches have straight, not wavy edges. The opening of each cell is at the 

 top of a little mound and there are several rows of cells across each branch. 

 C. carbonaria (fig. 290) is common. 



Fig. 290 



