No. 3.) JZOSCLES AND NERVES IN AMIA CALVA. 559 
2. Sub-Group 2. Muscles innervated by both the Trigeminus and 
Facialis. 
a. Intermandibularis. 
The intermandibularis (/m, Figs. 43 and 44, Pl. XXXI) isa 
short, stout muscle extending transversely from one ramus of 
the mandible to the other, immediately internal to the front 
end of the gular plate. Its fibres arise from the dentary of one 
side and are inserted on that of the other, the lines of insertion 
extending close up to the symphysis of the bones. Although 
to all appearance a single muscle, it can be easily separated 
along its front edge into two parts, each of which extends 
across the inter-ramal space and is thicker at its origin from 
the dentary of its own side than at its insertion on that of the 
other. The two portions are completely united posteriorly and 
overlap as the hyohyoidei do, the muscle of the left side lying 
superficial to or below that of the right. 
The superficial or inferior portion of the geniohyoideus, in 
passing from its origin on the mandible backward and inward 
toward the middle line of the head, lies partly superficial to the 
posterior portion of the intermandibularis; and the tendons 
of the deeper superior portion of the same muscle pass imme- 
diately dorsal to the intermandibularis closely attached to it. 
The branchio-mandibularis is either firmly attached to the 
hind margin of the intermandibularis or lies immediately dor- 
sal to it between it and the integument of the floor of the 
mouth. 
b. Geniohyoideus. 
The larger part of the geniohyoideus (Giz and Ghs, Figs. 
43 and 44, Pl. XXXI) lies immediately internal to the gular 
plate, which plate covers also the intermandibularis and the 
anterior portions of the sternohyoideus and hyohyoideus. 
The gular plate is a large and slightly convex dermal ossifica- 
tion about three quarters as long as the mandible (No. 3, G. 
Fig. 47, Pl. XLI). It is pointed in front, where it is firmly 
attached by ligament to the symphysis of the mandible, and 
