No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 723 
We thus have in the solid end of the basioccipital of the adult 
Amia all the parts of two vertebrae, or vertebral segments ; 
the longitudinal ligaments, the intermuscular septa, the lateral 
processes and ribs represented by the two occipital ligaments, 
the dorsal arches, the dorsal processes, and the ventral proc- 
esses. That still other vertebrae also have fused with the skull 
anterior to these two vertebrae is indicated by the nerves and 
muscle segments, and by the development of the occipitale 
laterale. 
4. Occipital Nerves and Corresponding Muscle Segments. 
From each of the spinal ganglia (gsf) in the adult Amia four 
well-developed nerves or branches arise (Fig. 35, Pl. XXIX): 
a dorsal branch (spd), which runs upward and backward along 
the posterior face of the septum in front of the segment to 
which the nerve belongs ; a horizontal branch (sp), which runs 
outward to, and then outward and backward along, the same 
face of the same septum, lying always above the horizontal 
septum between the dorsal and ventral muscles; a small 
branch (spa), which runs upward and backward, but mor- 
phologically forward, through the septum in front of the 
segment to join the dorsal branch of the second anterior 
spinal nerve; and a large ventral branch (spv), which runs 
downward and backward in front of the septum posterior to its 
segment, along the anterior edge of the rib that lies in that 
septum. 
In larvae the spinal ganglia lie wholly on the dorsal root of 
their nerve. The ventral root issues close to the ventral end 
of the ganglion, but does not touch it. Here it gives off the 
dorsal and horizontal branches above described, which are, 
respectively, the ramus dorsalis and ramus ventralis lateralis of 
von Lenhossék (No. 73, p. 173). It then turns downward to 
form the principal part of the large ventral branch of the nerve, 
the ramus ventralis medialis of von Lenhossék. The remaining 
portion of this ramus medialis is formed by a large nerve which 
arises from the ventral end of the ganglion of the dorsal root, 
and runs downward and slightly outward in front of the dorsal 
and horizontal branches of the ventral root. No fibres of this 
