190 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



4. Elongate form, with straight sides; very thin plates, perfectly 

 smooth, with small radial facets, deeply indented: P. planus Owen 

 and Shumard; Lower Burhngton; also found in the Mountain Lime- 

 stone of Belgium. 



Locality. — Button-mould Knob; also Lake Valley, New Mexico. 



5. Similar to the last, but with a few small nodes, forming lines from 

 radial facets to middle and corners of plates. 



Locality. — Button-mould and Bradbury Knobs, Kentucky. 



6. Elongate form, with slightly spreading sides; thin plates, very 

 small facets, but little indented in upper margin of radials; plates 

 evenly curved, but little depressed at the sutures. Very fine nodes 

 or tubercles, sometimes confluent, forming faint lines parallel to 

 margins of plates. One good calyx and detached plates. Is nearer 

 to P. granosus de Koninck and Lehon of the Mountain Limestone 

 of Belgium than to any American species, but may be compared 

 with P. scohina Meek and Worthen, Lower Burlington. 



Locality. — Button-mould Knob. 



7. Erect form, not elongate, slightly spreading; small facets, 

 directed upward; fairly thick plates with beveled sutures; rows of 

 moderate sized nodes run from facets to corners of radials: P.pocil- 

 liformis, Lower Burlington Limestone. 



Locality. — Wliites Creek; one good calyx. 



8. Erect form, large, spreading calyx; thin plates; facets wide and 

 shallow; ornamented with good-sized nodes, thickly distributed 

 without definite arrangement on basals and radials. 



Locality. — Button-mould Knob; similar form from Fern Glen, 

 Missouri, and Lake Valley, New Mexico. 



9. Elongate form, medium size, with spreading cup and stronger 

 plates than the preceding; ornamented with a few scattered nodes on 

 radials and basals; radial facets wide and shallow: P. verrucosus 

 Hall, Lower Burlington, but larger than usual at Burlington. 



Locality. — Button-mould Knob. 



10. Elongate, calyx moderately spreading; large, with strong plates; 

 radial facets wide; smooth, or slightly marked with obscure ridges: 

 P. scul'ptus Hall, Lower Burlington. 



Locality. — Button-mould Knob; Bradbury Knob; and Bell Knob, 

 near Lebanon, Kentucky. This is the only form that might perhaps 

 be referred to a Keokuk species of Platycrinus or Eucladocrinus. 

 Some plates from Bell Knob are more elongate than those at Button- 

 mould Knob, but similar variations from moderate to quite elongate 

 can be seen among specimens from Burlington labeled as above. 



n. Base of a small, smooth species, similar to P. hurlingtonensis 

 Owen and Shumard, Lower Burlington. 



Locality. — Stone's farm, Clark County, Indiana. 



