2 26 THE AMERICAN NATURALIST. [Vol. XXXVII. 



On my return to America, I began work anew on a few 

 fragments and isolated plates that had been obtained from Herr 

 A. Simonson, on my visit to the island of Oesel, and to which I 

 had previously failed to give adequate attention. One fragment 

 of special importance was almost concealed in the rock and its 

 true nature was not at first apparent ; the other was similar to a 

 plate first described by Rohon. When it became evident that 

 these fragments were probably parts of appendages, it was too 

 late to do more in that paper than refer to the fact that what 

 appeared to be fragments of appendages of Tremataspis had 

 been discovered. 



I shall now describe what I consider to be the distal portion 

 of an oar like appendage attached to the head of Tremataspis. 



