Oo 
=) 
bo 
DAVIDSON BLACK 
GANOIDEI8 
Motor nucler in Polyodon spathula 
An excellent account of gross features of the brain and of the 
superficial attachments of the cranial nerves in the Mississippi 
spoon-bill, has been contributed by Garman (27). Up to the 
present, however, no work has been published on the finer anat- 
omy of the brain in this animal. Among ganoids, the motor 
nuclei have already been studied and reconstruction charts have 
been made in the following forms: Amia (22 and 66), Lepidosteus 
and Acipenser (91). : 
Lob.vag, 
: Lob.vag. 
Fun.et trig.sp, NuVilim. 
RuVilimmasc.< 
Ey ~Tr.sec.com. 
\ 
Tr.sec.com. 
“Fib.arc.ext. = Tr.te.b 
18 19 
Figs. 18 to 24 Transverse sections of the brain of Polyodon spathula; figures 
19 to 24 drawn to the same scale. 
Fig. 18 Transverse section of brain stem at the exit level of the first motor 
spino-occipital rootlet. 
Fig. 19 Transverse section of brain stem at the exit level of the motor 
glossopharyngeus root. Abbreviations: C.c., crista cerebellaris; F.l.m., fascicu- 
lus longitudinalis medialis; Fib.arc.ext., external arcuate fibers; Fib.arc.int., 
internal arcuate fibers; Fun.et trig.sp., funicular area; Lob.lin.lat., lobus lineae 
lateralis; Lob.vag., visceral sensory column; N.U.1.X., nervus lineae lateralis; 
Nu.sp.oce.m., motor spino-occipital nucleus; Nu.VJ7.m., motor facial nucleus; 
Nu.X.m., motor vagus nucleus; ?.desc.V., tractus spinalis trigemini; R.sp.oce.m., 
first spino-occipital motor rootlet; R.VII.m.asc., ascending bundle of motor 
facial root; R.JX.m., motor glossopharyngeal root; 7'r.sec.com., secondary gusta- 
tory bundle; 7’r.tc.b., tractus teeto-bulbaris; Twb.ac., tuberculum acusticum. 
8 This term is retained because of its great convenience and is employed here 
in the sense defined by Jordan (55, p. 32). With regard to the literature on 
Polyodon, I am much indebted to Professor C. J. Herrick both for the loan of 
Garman’s paper (27) and for assistance during my vain search for any work 
dealing with the finer anatomy of the brain stem of this animal. 
