300 (J. II Gordon — Keokuk Beds at Keokuk. 



Genera. 





Total 

 Species. 



At 



Keokuk. 



At Craw- 

 fordsville. 



Spei 



;ies common, 



Synibathocrinus, 



Taxocrinus, 



Vasocrinus, 





3 

 3 



1 



3 



2 





] 



1 







Woodocrinus, 





6 



3 





2 







Zeacrinus, 





1 



-- 





-- 







Number genera, 



29 



128 



69 





32 





5 



From this it appears that over one-half of the species of the 

 formation occur at Keokuk, while at Crawfordsville the pro- 

 portion is about one-fourth with only five species common. 

 Out of the sixty-nine species observed at Keokuk, however, a 

 large portion are rarely met with, while the hardness of the 

 limestone matrix renders the collection and cleaning of fossils 

 a comparatively slow and difficult process. 



The collection of fish remains made here is an extensive 

 one and may be grouped as follows : 



Total Species Total Species 



Species, at Keokuk. Species, at Keokuk. 



Cochliodonts, 26 20 | Psammodonts, 1 1 



Hybodonts, 17 17 ] Ichthyodorulites, 16 13 



Pelalodonts, 20 14 — — 



Total, 80 65 



It is generally maintained against the evidence for the con- 

 trary from Coral Islands, as illustrated by Professor Dana, that 

 limestone is a deep-sea deposit. The appearance of the 

 Keokuk limestone in places shows very decided evidences of 

 having been subjected to shallow water conditions. That 

 littoral conditions are productive of arenaceous deposits alone 

 would seem to necessitate the further proof that the debris 

 derived from the neighboring land surface is distinctively 

 arenaceous in character. That this is generally so is readily 

 seen, but that it is always so can hardly be admitted. The 

 presence of crinoids in the Keokuk limestone has been accepted 

 as conclusive of a deep water origin, since existing forms of this 

 order are usually obtained far below the surface. Nevertheless 

 we are disposed to consider the Keokuk beds in the vicinity of 

 Keokuk as essentially a shallow water deposit. Toward the 

 east where it impinges upon the Cincinnati axis it becomes 

 decidedly arenaceous, but along its northern border in Iowa no 

 such change is observed, its calcareous character being as 

 marked as farther toward the south. Moreover the discovery 

 of a piece of fossil wood in this formation at Keokuk would 

 seem to imply (1) an adjacent shore line and (2) shallow water. 

 This interesting specimen was obtained from !No. 5, about 10 

 feet below the base of the Geode bed. It is a portion of a 

 Sigillarian trunk. 



Keokuk, Iowa, 



