DISCOID CRINOIDAL ROOTS AND CAMAROCRINUS 



FREDERICK W. SARDESON 

 Minneapolis, Minn. 



Since the writings of Wachsmuth and Springer,^ and of Bather* 

 have given an increased scientific interest to fossil Crinoidal roots or 

 stem bases, fossils of this sort which occur in the Galena (Trenton) 

 stage of the Ordovician in Minnesota, have been collected by me 

 with some especial care. In particular, certain disc-shaped roots 

 have been collected and studied. These are beheved to represent 

 the primitive form and structure of Crinoidal roots, and are of 

 special interest for that reason, as also because they are rare and 

 Httle known. Few fossils of this kind have been described heretofore. 

 Since my collection represents a relatively large number, about loo 

 specimens, and since they afford some new information regarding 

 the structure and relationship of such Crinoidal roots, description and 

 discussion of them is here offered. 



The specimens in hand are discoid or conical with fiat base, or 

 bent from that form when the surface to which the base had attached 

 is not plane. They are found adhering to shells, MonticuHporoid 

 stalks, Crinoid stems and especially to pebbles. They consist of 

 polygonal calcite plates in the manner of Echinoderms in general. 

 The center or apex of the cone bears a scar with central perforation. 

 This scar is Hke those which are characteristic of Crinoidal roots and 

 shows where a Crinoidal stem has been detached. In a few cases 

 an attached stem fragment remains. 



Among the specimens several species are represented, ranging 

 in structure from those similar to the well-known Lichenocrinus on 

 the one hand, and on the other to forms with lobate basal margin 

 which link rather to the well-known and common form of roots with 

 long, round cirri. Others tend to become globular and a relation to 

 the problematical Camarocrinus is therefore to be considered. 



1 The North American Crinoidea Camarata, p. 49-51, 1897. 



2 Geological Magazine, Vol. V, p. 328, 1898. 



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