362 HOWARD AYERS 
When seen from the side (fig. 18), the proximal part of the 
jaw bar stands perpendicular to the ventral bar. Where the 
upper lip joins the head the jaw bars bend from the vertical to 
a horizontal position and run forward in the ventral part of 
the upper lip just below the skin, converging as they go forward. 
Fig. 15 Dorsal view of the skeleton of the jaw apparatus of Ammocoetes, 
showing the jaw bars, bases of part of the tentacles, the large median tentacle, 
the extent of the hyoidean skeleton and outline of the lower lip. 
The vertical portions of the jaw bars form the elastic skeletal 
support of the buccal aperture. The basal median bar is a more 
or less cylindrical piece with its largest diameter where it unites 
with the jaw bars; here it gives off a short process which pro- 
jects forward and upward, swelling into a bulb or flask-shaped 
body with a slender neck crowned by a bush of tentacular branches 
