MONOGRAPH OF THE EXISTING CBINOIDS. 531 



Specimens with the radials about two-thirds as large as the basals: April 10. 



Specimens with the radials nearly as large as the basals: September 1; 

 November 9. 



Specimens with the radials just in contact in the posterior interradius: 

 January 12, September 1, November 9. 



Specimens with 12 brachials : June 25. 



Specimens showing the first appearance of interradials : September 1. 



Specimens with the interradials half as large as the radials; January 30, 

 November 9. 



A specimen nearly ready to discard the column : June 14. 



Expressing the same facts in another way, on the following dates the develop- 

 mental stages listed were found : 



January 12: (1) Specimens showing the beginnings of the radial structures; 

 (2) with the radials not quite in contact; and (3) with the radials just uniting 

 across the posterior interradius. 



January 28: (1) Specimens showing the beginnings of the radial structures, 

 and (2) with the radials just in contact. 



January 30 : ( 1 ) Specimens with the interradials half as large as the radials. 



February 7: (1) Specimens with the radial structures as yet undeveloped: 

 (2) showing the beginnings of the radial structures; and (3) with the radials 

 just in contact. 



February 8 : ( 1 ) Specimens with the radial structures as yet undeveloped, 

 and (2) with the radials just in contact. 



February 15: (1) Specimens showing the beginnings of the radial structures. 



April 10: (1) Specimens with the radials about two-thirds as large as the 

 basals. 



April 14: (1) Specimens with the radials showing considerable growth. 



April 17: (1) Specimens with the radials just in contact. 



June 14: (1) An apparently fully grown pentacrinoid. 



June 25: (1) Specimens with the radials just in contact, and (2) a specimen 

 with 12 brachials. 



July 31 : (1) Specimens with the radials just in contact. 



August 12 : ( 1 ) Specimens with the radials not quite in contact. 



September 1 : ( 1 ) Specimens with the radials nearly as large as the basals, 

 (2) with the radials just uniting across the posterior interradius, and (3) showing 

 the first appearance of interradials. 



November 9: (1) Specimens with the radial structures as yet undeveloped; 

 (2) with the radials not quite in contact; (3) with the radials just in contact; (4) 

 with the radials nearly as large as the basals; (5) with radials just uniting 

 across the posterior interradius; and (6) with the interradials half as large as the 

 radials. 



November 22: (1) Specimens with the radial structures as yet undeveloped. 



November 24: (1) Specimens with the radial structures as yet undeveloped. 



December 26: (1) Specimens showing the beginnings of the radial structures. 



