REPORT OF THE DIRECTOR T9TO 



^t5 



This would probably also indicate the order of their appearance 

 if plate increase was equal on all sutures. Plate a seems to have 



Fig. 3 Represents a small area of figure 2 still further enlarged. The dotted lines are ussd to 

 separate related groups of branchial vesicles. 



added more to its lateral than to its horizontal sutures and the 

 numbers used may thus fail to designate age. B.v. 6 was the last 

 formed and nos. 4 and 5 of the same group are so near to it that 

 they have hardly yet been separated from it. Continued addition 

 to the plate edges of this region would more and more separate 4 

 and 5 from 6, providing that the latter remained at the corner. The 

 distance between 3 and 6 being the greater, it is likely that an 

 additional 7th b.v. might make its exit on this side of 6 or that 6 

 itself would become forced to take up a position on the suture next 

 to 3. The b.v. at the extreme left angle of a, with the three nearest 

 to it form a group belonging to the right-hand member of the primi- 

 tive pair occupying the horizontal suture to the left of this point. 

 Conclusive evidence of such branching, forming groups, is not pre- 

 sented by this specimen, but it will be seen in Palaeocrinus and in 

 Palaeocystites. The dotted lines of figure 3 surround groups of b.vs. 

 which are supposed to be related as suggested above. 



