DISCOID CRINOIDAL ROOTS AND CAMAROCRINUS 249 



from zone No. 5, at St. Paul, IMinn. An associated species of Den- 

 drocrinus was the probable possessor of them. 



DISCUSSION 



In collecting specimens, I have not only obtained well-preserved 

 materials for the study of structures, but have tried also to find means 

 for identification of them. A root with entire column and crown 

 has not been found, and should scarcely be expected to occur where 

 all Echinodermal remains were badly scattered. But, roots and 

 associated stems can be matched with crowns more or less successfully 

 and careful effort to do this has been made. 



From the evidence which is afforded by the described specimens, 

 it may safely be concluded that these discoid stem-bases belong to 

 Crinoidea, and admitting circumstantial evidence, the conclusion 

 is imminent that they also belong to a diversity of Crinoidea. Calceoc- 

 rinus, Eucheirocrinus, Heterocrinus, and Anomalocrinus belong to 

 Bather's Order, Monocyclica Inadunata; Schizocrinus to Order, 

 Monocyclica Camerata; Dendrocrinus and Strophocrinus to Order, 

 Dicychca Inadunata. To the circumstantial evidence may be added 

 the fact that certain Cystidea have similar structures, the fixing- 

 plate in Lepidodiscus, which I have collected here, being very like 

 those of the Crinoidal discoid bases. This tends to prove that this 

 structure is primitive and might persist in diverse lines of Crinoidal 

 evolution. 



As to structure, there is conclusive evidence that the fixing-plate 

 in Podolithus is a single piece, while the top of the root is perhaps 

 always of many plates. If I understand rightly, Wachsmuth and 

 Springer^ considered the entire root or discoid base as a single plate 

 and compared it to the " dorso-central " plate of Antedon. Whether 

 the fixing-plate or the entire root should be now called dorso- central, 

 or perhaps neither comparison be made, I am not able to decide. 

 Again the interior presents always, as far as known, raised radiating 

 structures upon the fixing-plate and under the top plates, resembling 

 Lichenocrinus in the latter. Also as in Lichenocrinus, no pores or 

 canals to the exterior are seen aside from the stem-lumen and scar, 

 even though attached columnals present external pores. Accidental 



I Op. cit. 



