147 
wards on the inner surface of the abdominal wall, and just 
under the peritoneum. This ramus supples the ventral 
musculature and ventral skin. In the region of the 
appendages the limb: girdles and fins are supplied from 
R.R. ventrales. In the specimen now investigated, how- 
ever, the fourth spinal was not connected with either the 
pectoral or pelvic appendage. ‘The fourth R. ventralis 
anastomoses below with the nerve r. v. 2+3!, as described 
below. 
a hie rs tS inal, “N env er. 
This nerve is a compound of at least two spinal nerves, 
since it has two ganglia and most of its principal rami 
are in duplicate. It is, however, here described as the 
first spinal, on account of the difficulty of completely 
isolating its constituents. 
The ganglia and roots of the first spinal are situated 
in the bony tube formed by the exoccipital, and leading 
from the foramen magnum into the cranial cavity proper 
(see fig. 4). There is one main foramen for the nerve, 
which tunnels transversely the narrowed base of the par- 
occipital condyle, as shown in fig. 3 (above the lower letters 
Ke. O.). Another smaller foramen for the R. spinosus b. 
is situated immediately above this, and occasionally there 
is another larger one immediately below it for the R. 
ventralis, as shown in the chart. Usually, however, the 
latter nerve passes through the main foramen. ‘There are 
thus at least two foramina for the first spinal nerve, and 
there may be three 
all situated in the exoccipital. 
The first spinal has two perfectly distinct gangha— 
an intracranial ganglion (g. znter.), and an extracranial 
ganglion (g. evrter.). These two ganglia are connected by 
a large bundle of sensory and motor fibres which pass 
through the main foramen (indicated in the chart by the 
