i 



,43 



seven plates at each side of it. The latter are arranged like the 

 seven plates of the two inter-radial areas adjoining the anterior ray, 

 and as the radials of that side, as already stated, are arranged and 

 constructed like the special anal plates, the anterior side with its 

 two inter-radial series is almost a perfect counterpart of the anal 

 area. The uppermost anal plate is hexagonal or, perhaps, octagonal, 

 its upper side truncate ; its size is equal to, if not larger than, that 

 of the first radials. 



Acrocrinus Wortheni differs from the two previously described 

 species of this genus most conspicuously in the form of the basal 

 plates. The construction of the other plates is so imperfectly known, 

 that a comparison of other parts is impossible.* There is also a 

 great difference in the form of the body. 



The specific name is given in honor of Prof. A. H. Worthen, the 

 able Director of the Illinois Geological Survey. 



Geological position, etc : From the coal measures of Peoria 

 county. 111. 



The type is in the collection of Prof. Worthen. 



* The third part of the Eevision of the Palffioerinoidea, by Wachsmuth'and Springer, 

 will give a carefully revised generic description of Acrocrinus, and accurate diagrams. 

 The latter will be published also with this description in the 7th volume of the Illinois 

 Report. 



