284 WARD 



The following is a list of the twenty species of Cycadella in the 

 order in which they have been described : 



1. Cycadella reedii. 



2. Cycadella beecheriana. 



3. Cycadella wyomingensis. 



4. Cycadella knowltoniana. 



5. Cycadella compressa. 



6. Cycadella jurassica. , 



7. Cycadella nodosa. 



8. Cycadella cirrata. 



9. Cycadella exogena. 



10. Cycadella ramentosa. 



1 1 . Cycadella ferruginea. 



12. Cycadella contracta. 



13. Cycadella gravis. 



14. Cycadella verrucosa. 



15. Cycadella jejuna. 



16. Cycadella concinna. 



17. Cycadella crepidaria. 



18. Cycadella gelida. , 



19. Cycadella carbonensis. 



20. Cycadella knightii. 



The order can scarcely be called a classification. There is, how- 

 ever, something in common in the first twelve, viz., their general light 

 color and calcareous structure, while the last seven are darker, coarser 

 grained, and less calcareous. C. gravis and C. verrucosa are inter- 

 mediate in these respects, but the former differs in its high specific 

 gravity. These distinctions all relate rather to the mineral than to the 

 vegetable character, and although there is always some connection 

 between them as arising out of differences of structure, still it can 

 scarcely be called a systematic grouping. The strictly botanical char- 

 acters traverse these more conspicuous ones in such a manner that it is 

 impossible to arrange the species according to both, and it was con- 

 sidered more satisfactory upon the whole not to attempt any finer 

 classification until the internal structure can be studied, which should 

 be done and promises most interesting results. 



