61 



but most of the striie are destroyed on our specimen. All other 

 plates on the dorsal side curve over and cover part of the ventral 

 side. The ventral side is concave, and possesses a large oval space 

 covered with very numerous minute plates. The column is ellip- 

 tical, and has its shorter diameter equal to the greatest thickness 

 of the body. 



This species has oue plate less in the first range than there is 

 in P. sqitamosus, the species to which it would seem to be the 

 nearest. The rhombs are different in form from those belonging 

 to other species, and have their longer axes directed differently. 

 There are minor differences that will distinguish it from other 

 species also, and the general form will probably be sufficient in 

 all cases. We have used the family name Plcurocysfidd' pro- 

 visionally, without defining it, because this genus cannot belong 

 to the Lepadocrinida', where it has been placed heretofore. The 

 family relations among Cystideans are not well understood. 



Found by Prof. A. G. Wetherby, in the Trenton Group, in Mer- 

 cer County, Kentucky, and now in the collection of Wm. F. E. 

 Gurley. 



OKDER CYCLOCYSTOIDEA. 



Family CYCLOCYSTOIDID.E. 



CYCLOCYSTOIDES ILLINOISENSIS, n. sp. 



Plate V, Fig. 27, outer rim of a part of a specimen: Fig. 28, 

 outer rim of part of another specimen. 



This species is large and the outer rim is composed of a great 

 many plates. One of our specimens which does not appear to be 

 more than one-third of a circle, has nine plates. The other speci- 

 men, which does not appear to be much, if any, more than one- 

 half of the circle, has thirteen plates. The inference is that a 

 complete specimen will have from twenty-four to thirty plates. 

 The outer part or margin of the rim bears four or five rows of 

 elongated nodes, such as have not, we believe, been heretofore 

 found on any specimen. 



The great number of plates, in the rim, and the elongated nodes 

 on the margin will distinguish this species from all that have been 

 heretofore described. 



Found in the Hudson River Group on Orchard Creek, Alexan- 

 der county, Illinois, and now in the collection of Wm. F. E. 

 Gurley. 



