482 PAL.E0NTOLOGI0AL REPORT OF GEOLOGICAL SURVEY. 



the old Tariscon's mill, at the foot of the falls of the Ohio; and at 

 the crossing of the Jeffersonville and Columbus railroad, on Silver 

 creek, Clarke county, la. It has not been found extending beyond 

 this bed — which varies in thickness from five to twelve or thirteen feet. 

 Of the numerous specimens obtained by collectors, most of them are 

 mere fragments; very few have more than half or three-fourths of the 

 head complete — many not so much. This is the most abundant fos- 

 sil form of the bed at the locality on Beargrass. 



GENUS DOLATOCRINUS. Lyon. 



Gen. char. — Column, round ; composed (near the body) of alternate 

 large and small pieces; perforation pentalobate; rather large; basal 

 pieces five; pentagonal; small; sometimes covered by the column. 



First radials five, hexagonal; second radials five, quadrangular; 

 third radials five, pentagonal ; first secondary radials, ten or eleven, 

 generally hexagonal; second secondary radials quite irregular, varying 

 from ten to thirteen; interaxilarys, those rising from the radials from 

 five to seven, whilst those which rise from the interradial fields vary 

 from ten to twelve; interradials, first series, five, large nonagonal ; 

 the second series, of five, differing in form; arms ten, formed of circu- 

 lar pieces of equal thickness, tapering rapidly toward the superior end; 

 mouth sub-central proboscidate ; summit covered by small polygonal 

 pieces. 



DOLATOCRINUS LACUS. Lyon. 

 Plate IV. fig. 2, 2a, 26, 2c. 



Specific character. — Body sub-globose; truncated below; columnar- 

 pit broad and deep; summit somewhat conical, prolonged by a probos- 

 cis ; column round ; near the body composed of alternate large and 

 smaller pieces articulating by flat radiated surfaces; the upper joint 

 of the column is hemispherical, and partially fills the columnar-pit, 

 nearly and sometimes quite concealing the basal pieces; columnar per- 

 foration rather large and pentalobate. 



Basal pieces five;* pentagonal; nearly of equal size; not quite as 



•The basal pieces are only seen in fragments and crushed specimens; from these we are led 

 to believe that the basal pieces are five in number; should future investigation determine that 

 the base is divided into only three parts, the base would then resemble that of Platycrinus, 

 Miller, not Austin Being now fully pursuaded that this arrangement of five basals, alternat- 

 ing with fire first radials, is the structure of the animal, we have so described it. 



