RKPORT OF Jill': DIUl-XTOR KjJO 



229 



tion. A group of b.vs. was developed at the orad angle of each 

 IB and a group also at the aborad angle of each R. These ten 

 additional groups are all radial in position. To distinguish between 

 them we shall call one series orad and the other aborad. Text 

 figure 12 shows two of these groups, an orad radial group around 

 the aborad angle of a R 

 and an aborad radial 

 group around the orad 

 angle of an IB. The lat- 

 ter group will now re- 

 ceive our attention. 



The members of this 

 group occupy a triangular 

 area and are numbered 

 from I to 9. The evi- 

 dence here is for regular 

 serial formation with 

 counter-clockwise rota- 

 tion as in the interradial 

 group. For instance, we 

 have three b.vs. on the 

 left upper shoulder of the 

 IB and but two on the 

 right. The distance of 2 

 from the apex of the IB 



is greater than that of 3, Fig. 12 View of a portion of the holotype of Palaeo- 

 11 <• r -^ crinusstriatus Billings. From a photomicrograph, 



anCl tne distance 01 5 ^^ xio. The spiral Unes are drawn to indicate the order of 

 ,1 ,1 , c r -x development of the b.vs. 



greater than that of 6. In 



table 4 we have entered the measured distances of all these b.vs. 

 from the point in question, arranging those of each suture in a 

 separate vertical group as below. 









Table 4 







1 



1 . 8 mm 



2 



1 . 25 mm 



3 



1.15 mm 



4 



1-3 



5 



•7 



6 



.6 



7 



•75 



8 



•3 







9 



•3 











These distances have been plotted in figure 12 and a spiral line 

 drawn through them to more clearly express their serial formation 

 and its direction. 



