48 Trans. Acad. Sci. of St. Louis. 



ambulacral areas often acute and projecting beyond the sum- 

 mit. Column thin and round. Geological range from the 

 upper Silurian to the Coal Measures. The following species 

 belong to this genus : — 



1. CoDASTER ATTENUATUS, Ljou. Devonian. 

 Codaster attenuatus, Owen. 



Heteroschisma alternatum, Wachsmuth. 

 Heteroschisma alternatum var. elongatum, Wachsmuth. 



2. Codaster americanus, Shumard. Devonian. 



3. Codaster canadensis, E. Billings. Devonian. 



Codaster hindei, Whiteaves. 



4. Codaster gracilis, Wachsmuth. Devonian. 

 Heteroschisma gracilis, Wachsmuth. 



5. Codaster kentuckyensis, Shumard. Lower Subcarbo- 



niferous. 

 Pentremites kentuckyensis, Shumard. 

 Phaenoschisma, Etheridge and Carpenter. 



6. Codaster pulchellus, S. A. Miller and C. B. Dyer. 



Niagara gr. 

 Stephanocrinus puchellus, Miller and Dyer. 



7. Codaster pyramidatus, Shumard. Devonian. 



Codaster alternatus (pars), Lyon. 



8. Codaster subtruncatus, Hall. Devonian. 



Pentremites subtruncatus, Hall. 



Heteroschisma gracile, Wachsmuth. 



Troostocrinus subtruncatus, Etheridge and Carpenter. 



B. Order Irregulares. 



1. Family Olivanidae. 



1, Genus Olivanites. 



General form of the body oval or round. Base very small 

 and depressed. Fork pieces very short, hardly more than ^ 

 of the whole length of the body. Ambulacra narrow, linear 

 and extending the full length of the body. Deltoids very 



