142 SMITHSONIAN INSTITUTION 



PLATE LXVIII 



(AH figures natural size except where otherwise stated) 



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Figs. 1-6. Onychocrinus ulrichi Miller and Gurley 425 



(Also on Plates XXI, LXVI and LXVII) 



Fig. I. Ventral view of a large specimen, with rays widely spread ; part of tegmen, oral plates, 

 and anal tube preserved. 

 2, 3. Two less mature specimens showing the ventral structures. 



4. Ventral view of another large specimen, with interbrachials profusely developed and 



strongly contracted notwithstanding the rays are widely spread ; a more mature indi- 

 vidual than that of fig. i. Comparison of this with figures on this and preceding 

 plate shows that in addition to the extension of the rays there was a considerable 

 expansion and contraction of the calyx walls themselves due to up and down move- 

 ments of the viscera. 



5. Dorsal view of an expanded specimen showing the general form and proportions of calyx 



and rays when fully distended ; anal tube first impinging upon left posterior radial 

 before bending to the right. 



6. Reconstruction of the calyx, based upon the above and other specimens ; to show the 



ambulacra, oral and supporting plates, and the anal tube, in their probable positions 

 when the rays were spread and the orals closed (see also text-figure 8 showing varia- 

 tion in position of anal tube due to contraction of calyx). 



Keokuk Group, Lower Carboniferous. Indiana. 

 All from Indian Creek, Indiana, and in the author's collection. 1 



