72 



OHIO FOSSILS 



3. a 



b 



4. a 

 b 



5. a 

 b 



6. a 

 b 



7. a 

 b 



8. a 

 b 



9. a 

 b 



10. a 



b 



11. a 



b 



Outline of cup regularly oval Megacystites 



Outline rounded-triangular 3 



Plates few (13 only) Stephanocrinus 



Plates more than 13 4 



Top of cup flat Periechocrinites 



Top of cup tapering to a point Calliocrinus 



Arm bases projecting sideways from edge of cup 6 



Arm bases not projecting sideways from edge of cup 9 



Larger plates convex Habrocrinus 



Large plates nearly flat 7 



Plates striated or with rows of tubercles 8 



Plates not ornamented Periechocrinites 



Plates striated Marsupiocrinus 



Plates with 5 radial and many concentric rows of tubercles Caryocrinites 



Plates convex, with ridges radiating from the center Stribalocystites 



Plates flat and plain 10 



Cup conical Eucalyptocrinites 



Cup globe -shaped 11 



Cup more than 3/4 inch in diameter Lecanocrinus 



Cup less than 3/4 inch in diameter Pisocrinus 



CYSTOIDEA. The following descriptions include one genus of the subclass Blastoidea, 

 treated in some books as a separate class. 



Megacystite s greenvillensis (Holocystites in older publications) is regularly oval and 

 nas rows ot wart-like bumps along the edges of the plates (fig. 141). It 

 is found in the Guelph. 



Stephanocrinus elongatus (fig. 142) be- 

 longs to the subclass Blastoidea. It has only 

 13 plates on the cup and the upper ones are 

 forked. The cup is flat or pointed on top. It 

 is found in the Niagaran. 



Caryocrinite s ornatus ( Caryocrinus in 

 older publications) has conspicuous arm 

 bases; (fig. 143) the plates are flat, each 

 with 5 radiating and many concentric rows of 

 tubercles on each plate. It is fairly common 

 in the Cedarville and less so in the Guelph. 



Fig. 141 



Fig. 142 



Stribalocystites gorbyi (fig. 144) is 

 characterized by its convex plates. It occurs 

 in the Cedarville. 



CRINOIDEA. A key to both crinoids and cystoids has 

 been given at the beginning of this section. The commoner 

 genera and species of crinoids follow. 



Fig. 143 



Fig. 144 



