CHIXOTDS AND BLASTOIDS. 163 



CLASS PELMATOZOA. 

 ORDER CR1XOIDEA. 



SUBORDER CAMERATA. 



FAMILY ACTINOCRINID.E. 



GENUS ACTINOCRINUS. 



AtTIXOCRIXUS ORXATISSIMUS (llOY. Sp.) W. & Sp. 



PI. XVI, Fig. 9. A specimen with arms, showing the posterior side. 

 PI. XVII. Fig. 3. A specimen without arms; anterior view. 



This beautiful species has close affinities with Actinocrinus 

 tenuisculptus McChesney. from the Lower Burlington limestone, 

 which Hall redescribed in 1860, under the name of A. chloris. It 

 has a similar style of ornamentation, and the same number of 

 arms. 



In A. temrisculptus, however, the arms are arranged in clus- 

 ters, the interradial spares are wide and deeply depressed, and 

 this depression, which extends ventrally to the proximal plates, 

 gives to the calyx a decidedly lobed appearance not observable 

 in our species, neither dorsally nor ventrally. It also resembles 

 Actinocrinus ihiphne from the Waverly group of Ohio; but A. 

 ornutissimus has tooth-like processes on the back of the arms, 

 which are wanting both in the Burlington and Waverly species. 

 The specimens are always light colored. 



Dorsal side of the calyx somewhat depressed, sides convex as 

 far as the top of the secondary radials. whence they spread 

 more rapidly to the arm bases. Basals short; scarcely notched 

 along the sutures, extending outward and forming a rim. 



