168 JULIA WORTHINGTON. 
and its accompanying muscles, thus furnishing another proof 
of the statement made by Ayers and Jackson, 1900, that the 
tooth-plate represents the lower jaw, and not the tongue, as 
assumed by*Miiller and Firbringer. R. mandibularis, like 
r. maxillaris, consists of two divisions—an anterior and a 
posterior,—both of which contain both sensory and motor 
fibres. The anterior division consists of four branches, the 
first of which, r. dentalis, is a large, purely sensory nerve, 
running ventrad m. palato-coronaris and the wall of the 
pharynx to the tooth-plate, in which it subdivides profusely. 
The second branch is motor, and is small and slender. It 
divides almost immediately into a short posterior branch, 
running into m. copulo-quadratus profundus, and 
anterior branch running cephalad outside of r. maxillaris 
anterior, and on the inner face of m. copulo-quadratus 
profundus, to which it appears to give small twigs. It then 
runs on to m. copulo-ethmoidalis, and apparently ends 
there. The third branch is also motor. It sends a tiny twig 
into m. velo-quadratus, and then runs ventrad between 
m. palato-coronaris and m. copulo-quadratus-pro- 
fundus, supplying this latter muscle and m. hypo-copulo- 
glossus. Last of all is a small branch—motor and sensory 
combined,—the motor twig going to m. velo-quadratus, 
the sensory to the roof of the pharynx beneath. 
R. mandibularis posterior consists of two divisions. 
The anterior division, though mainly sensory, carries a couple 
of motor twigs to m. velo-quadratus. The sensory trunk 
runs between this muscle and the roof of the pharynx, 
sending twigs into the latter, and ending in the pharynx 
behind the first branchial arch. The posterior branch of 
r. mandibularis posterior is the great nerve supplying 
the muscles of the lower jaw, the “club muscle” and 
its accessories. It runs ventrad between m. copulo- 
quadratus-profundus and the pharynx, supplying the 
caudal part of this muscle and m. hyo-copulo-glossus 
(Firbringer’s r. pro. hyo-copulo-glossus), and then 
divides into two, an anterior branch, supplying m. copulo- 
