PAL/EONTOLOGtlUAL REPORT OF GEOLOGICAL SURVEY. 481 



Interradial fields. The interradial fields are four in number, each 

 filled with six pieces, differing in form and size; arranged by one 

 forming the base; from the sloping upper sides of this rise two others; 

 between these latter and their outer upper side, three others; upon 

 these rest the interaxilary pieces, eleven in number; these vary much 

 in form and size in different specimens. 



Nearly all the pieces composing the 2nd and 3rd primary radials, 

 and the interradial fields are flattened or slightly concave; this is char- 

 acteristic and common to the species. 



Anal pieces. The anal pieces vary much in different specimens — 

 from 14 to 18 of irregular form; being neither constant in form nor 

 number. 



The Arms vary in number from ten to fourteen, at their insertion 

 into the calyx; they are very irregular in their arrangement, some- 

 times coming off in five regular pairs; again three pairs — one set of 

 three, and one set of one, making ten; again, three sets of four each 

 one set of three, one of two, and a single arm, standing by itself, mak- 

 ing fourteen. 



Amongst the great number of the species that have come under 

 our-observation, no two have ever been observed with precisely the 

 same arrangement in the zone forming the region of the arms — suffi- 

 cient difference frequently existing, in different specimens, to warrant 

 a separation of the species if the technical arrangement should be re- 

 lied upon. By the low calyx, concave surface of the pieces, and gen- 

 eral appearance, they will, however, be referred oai species. 



Dimensions: 



Greatest heighth of calyx, - - - .-jVo- inch. 



Least heighth of calyx, - .^\ inch. 



Heigth from base to summit, ... .^jl inch. 



Greatest breadth, 1-tW inches. 



Least breadth, ..... 1-tVo - inches. 



Position and locality. Very abundant in the limestone immediate- 

 ly at the base of the "Devonian black slate," and above the beds of 

 Hydraulic cement stone. In the vicinity of Louisville, about fifty feet 

 above the range of Oatenepora escharoides bed. Actinocrinus ahnor-i 

 mis is especially abundant in the bed above alluded to, exposed at the 

 quarries, on the south fork of Bear grass creek; at Rook Island, near 

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