60 



THE AMERICAN MONTHLY 



[Feb. 



ond globular joint which extends between the paired 

 arms and bears a bristle-shaped spine. 



Dimensions: — 



Radius of the odd arm 0,17 m m. 



Radius of the paired arms 0.12 " 



Basal breadth of the paired arms 0.05 " 



Distal breadth 0.03 " 



Habitat: — Fossil in the rocks of Barbados. 



A duplicate of this form has been found by Rev. Fred. 

 B. Carter and as his form is identical, it is hardly proba- 

 ble that the second glohular joint could be one of the 



Cyrtida accidentally embedded in the shell. The pres- 

 ence of this appendage makes it doubtful if it belongs to 

 the genus Rhopalastrum. If it does not belong to this 

 genus, not only is the species new, but the genus, is new 

 to Barbados. 



