148 
oval dotted area). There was in the specimen sectioned 
a discrete patch of cells on the right side on the R. 
ventralis also, but in other examples these were con- 
tinuous with and part of the extracranial ganglion. 
We follow Fiirbringer and Herrick in designating 
the cephalic constituent of the first spinal by the letter ), 
and the caudal constituent by the letter ¢. It will be 
observed that the Plaice has three ventral roots instead of 
the two described by Herrick in Jenzdia,* and of these 
the extra one is undoubtedly the first (v. 6.1). 
The first spinal nerve of the Plaice has two dorsal 
sensory (mostly) and three ventral motor roots. Of the 
two dorsal roots the first (d. 6.) is larger than the second 
(d. ¢.), and arises obviously from the spinal vth tract. 
They both pass into the intracranial ganglion. Of the 
three ventral roots, the first (v. 6.1) is very long and 
slender, and fuses with the second (v. b.). The third (v. ¢.) 
is very short, and is the largest of all the roots. All three 
ventral roots pass into the intracranial ganglion. 
The following nerves arise from the intracranial 
ganglion :— 
1. R. spinosus, b (7. sy. 6.).—A motor nerve, arising 
from the fused first and second ventral roots. It passes 
through the intracranial ganglion, and leaves the exocci- 
pital by a small foramen immediately above the main 
foramen (indicated by a ring in the chart). It then passes 
forwards over the top of the extracranial ganglion, rises 
sharply at the side of the auditory capsule, and afterwards 
turns forwards over the roof of the capsule to supply the 
dorsal musculature and interspinal muscles. This nerve 
does not anastomose with a sensory R. communicans like 
the posterior RR. spinosi. 
*Stannius mentions only four roots in the Plaice also, having 
apparently missed the first ventral. 
