30 William Patten. 



laspis and Tremataspis is indicated by the resemblance in their median orbits, lateral and 

 post-orbital openings. 



The Asterolepidae and Tremataspidae are bound together more closely than before, 

 owing to their possession of oar-like appendages, large centrally placed orbits, and to the 

 arrangement of lateral line organs and oral plates. 



M. The Syncephalata : For the great phylum of the animal kingdom formed by the 

 union of the Vertebrates and the Arthropods, I propose the name Syncephalata. 



The delimination of the Syncephalata can be only roughly determined, especially at 

 the lower end of the phyllum. The main stalk consists of the Arachnids (including the Tri- 

 lobites, Merostomata, and Limulus, which were probably derived from Phyllopod-like Cru- 

 staceans); the Peltocephalata, and the Vertebrata, The point of divergence from the main 

 stalk of such groups as the Insects, Crustacea, and the simplified and aberrant forms like 

 the Ascidians, Amphioxus, Balenoglossus and others, are of minor importance and do not 

 concern us here. 



The justification of the term, Syncephalata, lies in the fact that in this vast series of 

 segmented animals the concentration and specialization of the anterior body segments into 

 a head region is definitely begun and completed. 



It is only when this group is viewed as a whole that we see these momentous struct- 

 ural advances in their true perspective, and can follow the endlessly varied theme that 

 leads steadily and consistently onward toward the completion of the most complex organic 

 structure that has ever been produced, the vertebrate head. 



