36 SMITHSONIAN INSTITUTION 



PLATE XV 



(All figures natural size except where otherwise stated) 



PAGE 



Figs. 1-8. Nipterocrinus wachsmuthi Meek and Worthen '. 203 



Fig. la. The type. Mature specimen with arras complete, cal3'x flattened and vertically crushed; 

 3 IBr and 8 or 9 IIBr. Mus. Comp. ZooL, Harvard. 

 16. Restoration of same, showing natural contour and length of arms; perisome restored from 



fig- 3- 

 2a, b. Two views of a similar specimen, somewhat flattened. 



3. Small crushed specimen, showing some of the perisomic integument between the rays. 



4. Base of crushed specimen with IBB separated from BB ; showing undivided inf rabasal 



disk. X 2. 



5. Specimen with nearly complete stem, showing a few radicular cirri. 



6. Smaller crushed specimen with part of stem. 



7. Crushed specimen, somewhat intermediate, with 6 IBr and 10 IIBr. 



8. Large specimen from lower part of Keokuk limestone, perhaps of this species. 



Upper Burlington limestone; Lower Carboniferous. Burlington, Iowa. 

 All specimens, except fig. I, are in the author's collection. 



Figs. 9-10. Nipterocrinus arboreus Worthen 203 



Fig. 9. The type, showing 4 and 5 IBr, and imbricated arms. University of Illinois. 



10a, h. Two views of very finely preserved crown, slightly flattened. It has the interbrachial 

 perisome intact, and extending to the third bifurcation ; 4 and 5 IBr ; and imbricated 

 arms. X 2. Author's collection. 

 IOC. Interbrachial area at " x " on fig. 106, showing detail of perisomic integument where it is 



partly broken away. X 3- 

 lod. Basal view of same specimen, showing undivided infrabasal disk. X 2. 



Lower Burlington limestone; Lower Carboniferous. Burlington, Iowa. 



