1^0 SMITHSONIAN INSTITUTION 



PLATE LXXII 

 (All fiarures natural size except where otherwise stated) 



PAGE 



Figs. I-I2. Onychocrinus ramulosus ( Lyon and Casseday ) 433 



Fig. I. The principal type specimen used in the original description; anterior view. From an 

 unpublished drawing made by Lyon accompanying his ^IS. It shows the long, stout 

 ray divisions and ramules ; 3 IBr ; and 4 or more IIBr. 



23. Posterior view of an extremely mature and remarkably perfect specimen ; showing the 

 relatively small anal tube, and the extraordinary development of higher interbrachial 

 structures, which continue in this specimen to the eighth axil ; the bilateral ramules 

 with subdivisions up to five ; and the profuse occurrence of arcuate sutures, with the 

 processes outlined so as to appear like plates. 



2b. A primary interbrachial area, constructed from a similar large specimen. 



3. Anterior view of a similar specimen, showing rays to their ultimate divisions. The inter- 



brachials in this and the preceding specimen, while abundant at the axils within the 

 rays, are relatively much less developed at the primary axil than in other species. 



4, 5. 6, 7, 8, 9. A series of younger specimens down to those in which no interbrachials whatever 



are found. . That of fig. 5 is labeled in the Lyon collection as from Barren County, 

 Kentucky. 



10. Section of a bent ray from IBr upward ground off on the curve, to show that notwith- 



standing their outward curvature and the appearance of " patelloid plates," the sutures 

 a short distance below the surface are perfectly straight. 



11. Abnormal specimen with left anterior ray unbranched. 



12. Abnormal specimen having 6 rays ; — an extra double ray being wedged in above the 



radials at the left posterior interbrachial area. 



Keokuk Gr. ; Lower Carboniferous. Crawf ordsville, Indiana, except as other- 

 wise stated. 



All specimens are in the author's collection. 



