REVISION OF STEREOCRINUS HARRIS. I03 



Vault around the pole consists of a moderate number of medium- 

 sized plates, among which the apical dome-plates are well developed, 

 and readily recognized by their large size. Anal aperture sub-central, 

 prolonged into a proboscis, consisting of thick small plates. Column 

 round, having the appearance of alternately thick and thin plates, but 

 really of the same size, and much depressed at the line of juncture; 

 central canal large, pentalobate. 



Observations : In the Proceedings of the Davenport Acad. Nat. 

 Sci., Vol. II., p. 282, the author described two species of Stereocrinus, 

 accompanied with appropriate illustrations. Attention was then given 

 solely to specific differences, and no attempt was made in the way of 

 generic description, other than the enunciation of the most meagre 

 formula. It is to remedy such defect that the above generic descrip- 

 tion is given. 



A large number of specimens which had been gathered from the 

 Davenport locality, and a still larger collection subsequently made 

 from Alpena, Michigan, were sent to Mr. Charles Wachsmuth, of Bur- 

 lington, Iowa, who, after careful examination, defined the status of 

 Stereocrinus as a siib-genus of Dolatocrhiiis, and thus announced it in 

 Part II. of his great work on the Revision of the Pak-eocrinoidea. 



The range of this genus, as far as known, seems restricted to the 

 Hamilton of Iowa and Michigan. In the course of his studies, Mr. 

 Wachsmuth had occasion to examine the most extensive collections 

 of Dolatocrinus from the celebrated Beargrass locality of Kentucky, 

 among which he failed to find a single specimen of Stereocrinns. 



Subsequently the entire collection of the Blastoids and Crinoids of 

 the geological survey of Canada passed through his hands for examina- 

 tion and identification. He writes that while there were several new 

 species of Dolatocrintis, there were none of the species described in 

 this paper, nor was there a trace of Stereocrinus. 



Local peculiarities, such as differences in form and size, characterize 

 this crinoid in each locality where it is found. In the quarries west of 

 Davenport, the prevailing form is cup-shaped, with moderately broad 

 base, high curved sides, and prominent dome. In addition, it attains 

 a notably large size, in this respect rivalling the Alegistocrinus, with 

 which it is associated. These characteristics are well brought out in 

 the illustrations accompanying the original descriptions.* 



*See Proc. Dav. Acad. Nat. Sci., \'ol. II., plate 11. 



