1^.6 SMITHSONIAN INSTITUTION 



PLATE LXX 



(All figures natural size) 



PAGE 



Figs. 1-7. Onychocrinus exsculptus Lyon and Casseday 430 



(Also on Plates LXIX and LXXI) 



Fig. I. Posterior view of a very mature and perfect specimen, showing all the characters of the 

 species ; especially the anal structures, the long, tapering ray divisions and delicate 

 ramules. The rami are united to third range above axillary. 



2. Similar specimen, anterior view ; showing the interbrachial structures with their crescentic 



distal margin in perfect condition. 

 20. Diagram of a ray, showing decrease in number and size of ramules distally. 



3. A less mature specimen, with stem nearly complete, showing scattered cirri toward the 



distal end; rami united for two ranges. 



4. S, 6, 7. A series of successively younger specimens with interbrachials diminishing to one 



plate, and the rami finally united by only part of one pair of plates. The juvenile 

 character of the stem is well shown in figs. S and 6, where it rapidly passes into long 

 columnals. 



Keokuk Gr. ; Lower Carboniferous. Crawfordsville, Indiana. 



All the specimens are in the author's collection. 



