486 ALLIS. [Vou. II. 
System II. is a double one formed at the point where the 
mandibular and opercular parts of the canal unite. Its primary 
branches are widely separated, one of them lying in the angu- 
lar, near the upper end of the bone, and the other in the thick 
dermis between the angular and pre-operculum. The former 
has twenty-eight openings, eighteen in the angular and two in 
the supra-angular; and the latter, seven, all in the dermis, 
making twenty-seven in all for the entire system. 
In the opercular part of the canal, the trunks of five peripheral 
systems are given off, Nos. 12 to 16, all of them running out- 
ward, and backward or downward, toward the outer edge of the 
bone, where each has several large irregular openings, approxi- 
mately thirty-four in all. Trunk 17, the last one of the line, 
has united with 17 infra-orbital, as already described, to form a 
double trunk and system which lies wholly in the dermis be- 
tween the pre-operculum and squamosal. 
The mandibular canal in Micropterus dolomeus and in Salve- 
linus namaycush passes through the articular, and not through 
the angular, as in Amia and in Polypterus (No. 18, p. 182). In 
those two teleosts the angular is a small bone lying below or 
behind the articular, which is large and has the same position 
relative to the dentary that the angular has in the two ganoids. 
The articular in Polypterus is small, and lies below and behind 
the angular; and in Amia, what Bridge has called ossicle holds 
a corresponding position. This ossicle is, according to him, 
formed by the ossification of the hind end of Meckle’s cartilage. 
It is covered by a small ganoid plate; and Bridge suggests that 
it may represent, at least in part, the articular of teleosts. But 
neither it nor the overlying dermal plate is traversed by a lateral 
canal, while the angular is. This last bone in the ganoids has 
doubtless been so called because it is entirely dermal, agreeing 
in this respect with the angular in teleosts, and differing from 
the articular, which has been supposed to be always pre-formed 
in cartilage. As the teleostean articular is in some forms trav- 
ersed by a lateral canal, this distinction does not hald good, and 
the names now used for the bones in the ganoids should proba- 
bly be changed. 
6. Summary.—In this specimen, which is strictly a normal 
one, there are in all xznety-three peripheral canal-systems, forty-six 
on each side of the head, and a median one in the supratemporal 
