Palaeocrinus striatus Billings 



The figures are from photomicrographs of the holotype xio and 

 taken under a mounting of gum dammar. They are here repro- 

 duced without retouching. Each figure is from a separate negative. 

 Figures i and 2 show this surface as it was when Mr Billings made 

 his description. 



Fig. 1-2 Radianal and adjacent plates. That the radianal is four 

 sided instead of six, as heretofore figured, may be here 

 clearly seen. The approach to an angle on the lower 

 right margin (next r.post.B) is due to the bowing out 

 of the plate and the angle from which this curved sur- 

 face is seen. The effect is very like that of a meridian 

 on a globe photographed at an angle. The cross sec- 

 tions of carbon lined sutural canals on upper margins of 

 post.B are fairly well shown. 



3 A view of this region after the removal of a layer about 



0.1 mm thick from a small area of the X and RA 



4 A view of the same area after the removal of an additional 



thin layer. The thickness of the last layer removed was 

 from o mm at the right to between o.i and 0.2 mm at the 

 left. The area of subthecal tubes is seen to be more ex- 

 tended at the left. A yellow color screen was used for 

 this negative 

 Figures 3 and 4 do not reveal the finer detail of sections of 

 supposed diverticula from the rectum which is shown in the 

 photomicrographs. If it be remembered that in these figures the 

 area around the suture between RA has been cut down with a file 

 and that such features as show are subthecal the figures may still 

 show features of interest. 



270 



