2^2 



FREDERICK W. SARDESON 



Figs. II, 13, 17, and 18. These bases are evidently very plastic to 

 environmental conditions and certain characters in them if increased 

 under exceptional conditions might well have changed to such as 

 Camarocrimis possesses. Those characters are the occasionally turned- 

 under margin (Fig. 13), and the five or more depressed spaces of the 

 top surface (Fig. 19). These depressions may be termed inter- 

 radicle pockets, since they lie between the main canals and lobes 

 which radiate from the corners of the stem and lumen, or between 

 branches of the same, all of which may be termed radicles. 



A series of diagrams are given here to help show the probable 

 origin of Camarocrinus (Fig. 31) from a discoid root (Fig. 27). 



Figs. 



27-31 



•^ 30 



Taking the pentameral symmetry as typical, then a vertical section 

 passing through a radicle, r, on one side, would cut the inter-radicle 

 i on the other side. The respective inter-radicle and radicle contours, 

 not cut by the plane of the section, are drawn in broken lines. Since 

 Camarocrinus is supposed to have floated in inverted position, it 

 should be represented so, except that comparison is easier when all 

 figures correspond. Fig. 27 represents a known discoid base with 

 normal, wide fixing-plate, /, and shallow, inter-radial pockets, c. 

 Fig. 28 represents it with the margin turned under because of limited 

 ground. Fig. 29 is an hypothetical representation of the same attached 

 to a floating object by still more Hmited area, so that a smaller fixing- 

 plate, /, and deeper pockets, c, result. Fig. 30 represents an adapta- 

 tion where the supporting object and fixing-plate are less in surface 

 and the pockets — gas filled — are enlarged. Fig. 31 represents Cama- 

 rocrinus with fixing-plate, /, very small, not larger than other plates, 

 while the pockets, c, are correspondingly enlarged and approximated. 



