The Cranial Nerve Components of Petromyzon. 
203 
The following abbreviations are used in both text figures 
and plate: 
a aorta, 
ac tubereulum acusticum, 
au.c auditory capsule and organ, 
br brain, 
ch notochord, 
d.t dorsal twigs from the trigeminus 
ganglion, 
f.e fasciculus communis, 
g.acust ganglion of the VIII. nerve, 
g.acust.fae intra-capsular ganglion of 
the VII—VIII complex, 
giph Nervus glossopharyngeus, 
g.tr ganglion of the trigeminus, 
i-o.n infraorbital row of pit organs and 
the nerve supplying them, the ra- 
mus bucealis, 
l.! Nervus lineae lateralis, 
l.m.c lateral (visceral) motor column 
in the medulla oblongata, 
l.v lobus vagi, 
m body muscles, 
m.tr motor root of the trigeminus, 
n neuromast or lateral line roots of 
the VII—VIII complex, 
n.a neural arch, 
N.o Nervus opticus, 
N.olf Nervus olfactorius, 
N.prof Nervus ophthalmicus profundus, 
n.t neuromast twig from the profundus 
ganglion, 
ph pharynx, 
ph.m pharyngeal muscles, 
pit.o pit organs of the lateral line 
system, 
pr.a.n.g pre-auditory neuromastganglion 
of the VIT—VIIL complex, 
prof ophthalmieus profundus nerve and 
ganglion, 
pseud.br pseudobranchial groove, 
r.b ramus buccalis, 
r.d ramus dorsalis of spinal nerves, 
r.kyom ramus hyomandibularis, 
r.man ramus mandibularis, 
r.maxz vYamus maxillaris, 
r.m.cut ramus musculo-cutaneous of 
the glossopharyngeus and branchial 
nerves, 
r.o.s elements representing the ramus 
ophthalmieus superfieialis V and VII, 
r.v ramus ventralis of the spinal nerves, 
r.vise ramus visceralis of the glosso- 
pharyngeus and branchial nerves, 
s-o two pit orgaus belonging to the 
supraorbital row innervated by the 
dorsal neuromast twig from the pro- 
fundus ganglion, 
s-o.n supraorbital row of pit organs 
and the nerve innervating them, 
sp.V tractus trigemini spinalis, 
sp.d.1,2, ete. dorsal spinal nerves, first, 
second, etc., 
sp.v.1,2, ete. ventral spinal nerves, first, 
second, etc., 
s.tr sensory root of the trigeminus, 
sym sympathetie trunk and ganglia, 
t.b taste buds in the pharynx, 
tr.epib truncus epibranchialis (»vagus 
trunk«), 
vel velum, 
v.m velar muscle, 
X,br.1.2,ete. the branchial nerves of 
the vagus complex, 
1,1a,1b,2, 3, 4,5,6,7,8,9 voots of the IX 
—X complex, 
VI the nerve which is usually called 
the abducens. 
