l88 THE AMERICAN MIDLAND NATURALIST 



fossils of the Owen substage, those of the Spirifer zone, and those of 

 the Striatula zone. Even this division, however, fails to give the 

 true distinction between the last two subdivisions; this is apparent 

 only in survey of the results of several days of careful collecting. 

 It is a diiTerence not so much of species as of numbers of species, 

 and numbers of individuals, there being a greater abundance of 

 both in the Spirifer zone. 



In the following list, the abbreviation "sp." is used where the 

 species is undetermined; the abbreviation "n. sp." indicates that 

 the species (or variety: "n. var.") is undescribed. 



Fossil Species of the Owen Substage. 



PI.ANTAE 



"Fucoids," of at least two species, undetermined. 

 ANIMALES. 

 Porifera 



Cliona sp. or sps. Large boring forms in Alveolites, Acervu- 

 laria, Pachyphyllum, etc. 

 Coelenterata 

 Anthozoa 



Heliophyllum sp. 



Heliophyllum n. sp. 



Chonophyllum ellipticum H. & W. 



Chonophyllum sp. 



Zaphrentis solida H & W. 



Cystiphyllum mundulum H. & W. 



Charactophyllum nanum (H. & W.) 



Strombodes johanni (H. & W.) ^ 



Strombodes johanni multiradiatus (H. & W.) 



Acervularia cf. inequalis H. & W. 



Acervularia n. sp. 



Acervularia n. sp. 



Pachyphyllum woodmani (White) 



Pachyphyllum woodmani (White) var. 



Pachyphyllum crassisostatum Webster 



Pachyphyllum crassum Webster 



Alveolites rockfordensis H. & W. 



Cladopora robusta Rom.? 



Aulopora iowensis H. & W. 



Aulopora cf. saxivadum H. & W 



