13 



This species is remarkable for the great height of the vault 

 and large proboscis, in proportion to the size of the calyx. It 

 is also remarkable for the number of arms and their bifurcations. 



Found in the Keokuk Group, in Greene county, Illinois, and 

 now in the Illinois State Museum and numbered 2594. 



Actinocrinus lobatus was described by Hall, in 1859, in his 

 Supplement to the Geology of Iowa, page 51, without an illus- 

 tration. It has never been illustrated, and we are not sure that 

 we have ever seen a specimen of it. The vault is described as 

 "irregularly convex above," while this species is remarkable for 

 its conical vault and extremely large proboscis. The calyx is 

 described as "distinctly divided into lobes by the depression of 

 the interbrachiai and anal spaces," which is not the case in this 

 species. That species could not "have had more than twenty- 

 five arms," while this species has not less than thirty. That 

 species has four regular interradials in the fourth range, while 

 this species has only three. The surface of the plates, in that 

 species is traversed by "sharp ridges," in this species the ridges 

 are low and broadly rounded. The nodes on the radial series, 

 in that species are transverse, in this species they are longi- 

 tudinal. The ridges "from the first radials to the basal plates 

 are four," in that species, in this species there is only one; those 

 from one first radial plate to the other in that species are two, 

 in this species only one; those from the first radial to the sec- 

 ond, in that species are two, in this species there is only one. 

 Hail compared that species, with Actinocrinus lowei, from which 

 he distinguished it in a few minor particulars, but this species 

 is so far removed from A. lowei in every important particular, 

 that no one would think of comparing the two. There are no 

 two species of Actinocrinus farther removed from A. lowei and 

 A. lobatus, than the one here under consideration, and we are 

 quite at a loss to understand why the late distinguished palae- 

 ontologist, Prof. Worthen, should have thought of identifying 

 this species with either one of them. The mistake may have 

 been overlooked because he died before the publication of the 

 work. 



