THE AMERICA* XA Ti T RA LEST. [Vol. XXXV 1 1 . 



they are indeed somewhat similar. Both plates have a strongly 

 convex outer surface, a pointed posterior extremity and an artic 

 ulating anterior margin. In Figs. 7 and 8 I have reconstructed 

 the appendages of Tremataspis on the assumption that the basal 

 portion was covered by several plates similar to those of Bothrio- 

 lepis. In these figures the basal and distal parts of this hypo- 

 thetical appendage and also, as far as possible, the marginal 

 incision of the cephalic shield, are drawn to the same scale. I 

 have described this incision in my first paper and have shown 



that it lies on the down turned margin of the shield. I assume 

 that the collar of the basal plate with its convex side facing 

 dorsally, was attached by ligaments, or a flexible membrane, to 



likely that the collar of the basal plate actually fitted into the 

 incisions, for its surface is not smooth enough, and if it did there 

 could hardly be the requisite freedom of movement. 



