668 Springer- — Mysticocrinus. 



Two specimens of this singular form have been discov- 

 ered — one the nearly perfect type here figured, which is 

 about 5 mm. in diameter, and a fragment of another one 

 somewhat larger. The seven enlarged figures made 

 from direct photographs furnish the evidence upon which 

 the diagram of the detailed structures is constructed. 

 Aside from the remarkable and unprecedented combina- 

 tion of general characters, the most striking feature is 

 the distribution of the processes on the anal and radial 

 plates in such a way that there is an arrowhead projec- 

 tion between the arm bases in every interradial area. 

 The arms are preserved in three rays to what is prob- 

 ably almost if not quite their full length ; from their taper, 

 and the manner in which they infold closely over the teg- 

 men, it is doubtful if they extended farther than is 

 indicated in the diagram, where the brachials which have 

 been lost are represented by parallel hatching. The 

 pentamerism of the calyx is remarkable for a certain reg- 

 ular irregularity, yet if we leave out of consideration the 

 radianal it is bilaterally symmetric. The large anal 

 plate with its angular projection distal wards recalls that 

 of Lecanocrinus among the Flexibilia. 



The specific name is given in honor of Dr. Herrick E. 

 Wilson, who found the type specimen among extensive 

 collections made for me in the vicinity of St. Paul, Indi- 

 ana, which have yielded a number of other extremely 

 interesting new forms yet to be described. 



DESCRIPTION OF PLATE II 

 Mysticocrinus wilsoni n. sp. (All figures x 8.) 



Fig. 1. Posterior view of crown, showing anal plate with its arrow-shaped 

 projecting apex, and lower brachials of the two posterior arms. 



2. From left posterior radial, showing interbrachial process on left 



half of plate. 



3. Left anterior radial, without projecting processes. 



4. Anterior radial view, showing projecting process on each side. 



5. Eight posterior view, showing the compound radial, with RA, fol- 



lowed by r.post.E., with projecting process on right half of 

 plate. 



6. Basal view, showing the concave infrabasals. 



7. Distal view, showing the short, infolding arms. 



8. Diagram of calyx, with arms so far as preserved; missing plates 



indicated by parallel hatching. 

 (Specimen here figured is in the author's collection.) 



