THE ANTIARCHA. 



369 



oral surface, and in side views it then appears to be absent. A branch of the 

 suborbital Une extends over this plate, apparently connecting with the sensory 

 groove of the premaxilla. (Figs. 254, 262, mx.) 



Fig. 248. — Restoration of Bothriolepis canadensis. (Whiteaves.) HsEmal surface. About i /2 natural size. 



The remaining plates of the pro- and meso-cephalic shield, except those 

 in the orbital opening, are practically immovable, and are frequently found as one 

 piece, even when all the other plates have separated through maceration. 



The hranchiocephalon enclosed the gills, atrial chamber, viscera, and repro- 

 24 



