328 ROY L. MOODIE 
Fig. 3 The condition of the spicules of bone around the supra-orbital canal 
of larval Amiurus, 24.2 mm. in length. The heavy nature of the walls is due to 
the fact that many spicules are seen superimposed. /fr., frontal bone, the ossifi- 
cation of which takes place at the same time as the other bones which are in- 
fluenced by the canals. The letters fr are placed at the midline of the head. 
ot. otolith. sp. c¢., supra-orbital canal at the point of junction with the suborbi- 
tal canal leading off to the right. sph. the initial deposition of radiating spicules 
at the point where the sphenotie will later form. 
Fig. 4 The suborbital chain of bones on the suborbital canal (sbo.) at the 
region of its junction with the supra-orbital canal in an Amiurus larva 50 mm. 
in length, showing the condition of ossification in the threads and granules. 
Above the index line leading to the letters sbo. the granules are arranged in a 
ring protecting the tubule opening from the canal at this point. 
