734 ALLIS. [Vou. XII. 
surface of the septum posterior to that segment or imme- 
diately behind that septum. It always has a double dis- 
tribution, going in part to the posterior segment of the 
sternohyoideus and in part to the pectoral fin. In some 
specimens it separates into two parts, one going directly to the 
posterior segment of the sternohyoideus, and the other joining 
and fusing with the ventral branch of the nervus postoccipi- 
talis, or first spinal nerve. In others it touches and anasto- 
moses with, or receives an anastomosing branch from, the ven- 
tral branch of the third occipital nerve, and then joins the first 
spinal nerve, or the contrary, anastomosing with the first 
spinal nerve, and then sending a branch to the sternohyoideus. 
The branch that goes tothe sternohyoideus accompanies closely 
the united ventral branches of the first, second, and third 
occipital nerves, running sometimes, with those nerves, internal 
to the pharyngo-claviculares, but sometimes perforating the 
internal one of those two muscles. It always gives off one or 
more general cutaneous branches, one of which either perfo- 
rates the pharyngo-clavicularis internus, or passes around the 
anterior edge of that muscle to its outer surface. The nerve 
then enters the posterior division of the sternohyoideus along 
its median face. 
The ventral branches of the first spinal and last two occipi- 
tal nerves often separate, in dissection, into two strands, and 
the two strands of one or more of the nerves may be found 
issuing as separate nerves from the trunk muscles. This is 
often confusing, and to be certain of the number of nerves 
under consideration, the dissection must always be carried to 
the ganglia themselves. 
There are thus in Amia, in the adult, five muscle segments 
and five intermuscular septa in the postauditory region of the 
skull. In larvae there are but four. The sixth intermuscular 
septum, in the adult, is attached to the first vertebra, and the 
sixth muscle segment extends from it to the fifth septum, 
which is attached to the hind end of the skull. In larvae it is 
the fifth septum and segment that have that position. If the 
intermuscular septa are vertebral, as is generally conceded, the 
five postauditory septa of the adult must indicate five vertebrae 

