No: 3:] USCLES AND NERVES IN AMIA CALVA. 683 
accordingly, homodynamous with the interbranchiales of sela- 
chians, and not with the interbranchiales of Chimaera and the 
levatores arcuum branchialium of other fishes. The levator 
maxillae superioris, on the contrary, develops from the deeper 
portion of the constrictor and is the serial homologue on its 
arch, whatever that arch may be, of those muscles. The 
adductor mandibulae lies along the outer surface and anterior 
edge of the arch, excepting in its ventral portion, where it is 
inserted in part on the inner surface of the arch. The nerve 
and artery of the arch lie along the anterior surface of the 
muscle, as they do along the anterior surface of the inter- 
branchiales in Chimaera. The middle portion of that muscle 
has accordingly, in the mandibular arch, slipped over the 
anterior edge of the arch, instead of over its posterior edge, as 
on the branchial arches. The adductor mandibulae is thus not 
strictly homodynamous with the adductores arcuum branchia- 
lium. The geniohyoideus and intermandibularis are probably 
the obliqui ventrales of their arch or arches. 
7. WNervus Glossopharyngeus. 
The nervus glossopharyngeus ( g/, especially Figs. 25, 52 to 
55,and 64, Pls. XXV, XXXIV, XXXV, and XXXVIII) arises, 
in the adult, by a single root from the side of the medulla 
oblongata, immediately ventral to and a little posterior to the 
root of the nervus lineae lateralis vagi. It runs at first out- 
ward and backward across the ventral surface of that root, and 
then turns outward, backward, and downward immediately in 
front of the middle membranous portion of the posterior 
bounding wall of the labyrinth recess. It passes above the 
ramulus papillae lagenae acustici, under the ramulus ampullae 
posterioris acustici, between the sacculus and the sinus utriculi 
posterior (Fig. 57, Pl. XX XV), and issues from the cranium 
by its foramen (g/f7, Figs. 9, 10, 11, Pl. XXI), which lies 
immediately behind the hind edge of the petrosal, in the angle 
between that edge and the ventral edge of the posterior process 
of the bone. The foramen lies entirely in the cartilage of the 
cranium, but its front and upper edges are formed by the 
petrosal. 
