^04 PROCEEDinas OP THE TfATtOJJAL MUSEUM. vol.41. 



clays below the level of any of the fossil-bearing beds. It has always 

 been credited to the Keokuk, and this may be correct. It is similar 

 to Z. compactilis Worthen, from Cumberland County, Kentucky, the 

 only known specimen of which is labeled Keokuk. The form of 

 base in these two species is unknown in the Burlington rocks. 



STEMMATOCRINUS Trautschold. 



S. trautscholdi Wachsmuth and Springer.^ This remarkable species 

 was described by us from a large series of specimens collected by 

 Wachsmuth at Whites Creek. They were nearly all found in one 

 locality, a plowed field in a valley filled with soil washed from the 

 hills, some distance from the Keokuk exposures. Doctor Bassler 

 and Mr. Braun also found several specimens, but none of them in 

 place; all were in position where it was possible for the loose fossils 

 to have been derived from either horizon. The genus was first 

 observed in the Bergkalk of Moscow, Russia, whose crindidal fauna 

 closely parallels that of our Kaskaskia; and the only occurrence of 

 it in this country is that of the present species, which has been sup- 

 posed to be from the Keokuk. It has not been found in Barren 

 County, or other Keokuk localities in Kentucky, or elsewhere; only 

 at Wliites Creek until now. I find loose plates of it in the debris of 

 the Knobstone shales at Button-mould Knob, not associated with Keo- 

 kuk fossils, and I think this establishes a presumption that its true 

 horizon is Knobstone rather than Keokuk. But I state this impres- 

 sion subject to change upon further evidence. 



BLASTOIDEA. 



The genera and species of this order are usually excellent indices 

 of stratigraphy, being restricted mostly to very definite limits. 

 Although not abundant in these rocks, we are fortunate in finding 

 a few which are of decisive weight. 



OROPHOCRINUS von Seebaeh. 



This genus was short lived, and confined, so far as known, to the 

 Kinderliook and Lower Burlington and their equivalents. In the 

 very rich blastoid fauna of the Upper Burhngton it does not occur, 

 unless in the doubtful species, Pentremites sirius Wliite, and in the 

 Keokuk not a trace of it has ever been seen at any locahty. It is 

 therefore extremely significant that we find at Button-mould Kjiob 

 the detached forked-plates of a large species of Oropliocrinus of the 

 same type as the well-known 0. stelliformis of the Lower Burlington. 



> Rev. Pal., vol. 3, p. 256. 



