No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 7O7 
arises from the dorsal aorta, traverses its canal, runs upward, 
outward, and forward along the lateral surface of the basioc- 
cipital and then of the occipitale laterale, and then inward 
along the dorsal surface of the latter bone. It apparently 
receives branches from all the prespinal muscle segments, but 
this was not definitely established. In 20 mm. larvae it lies 
wholly outside the cartilage of the base of the skull, passing 
through a region where membrane bone is forming, internal to 
the parasphenoid. 
Immediately posterior to the ventral openings of the two 
canals, above described, there are, on the ventral surface of 
the basioccipital, on each side of the middle line, one or two 
slightly projecting processes of cartilage (vp°). The posterior 
of these two processes is always found, and has been described 
by Sagemehl (No. 104, p. 195). The anterior one, which is 
sometimes wanting, and is sometimes fused with the posterior 
one, to form a single elongated piece or process is not 
described by him. The posterior process lies on the posterior, 
vertebra-like, terminal piece or portion of the basioccipital ; the 
anterior one lies immediately in front of the groove or line sep- 
arating that posterior portion from the anterior portion of the 
solid end of the bone. Sagemehl states that these little cartil- 
aginous processes correspond to similar processes found on the 
ventral surfaces of all the vertebrae. This statement I can 
confirm for the six anterior trunk vertebrae. On the vertebrae 
of the tail, which unfortunately I have been unable to examine, I 
am inclined to think the processes become the ventral arches, 
which is evidently not what Sagemehl intended to state. It 
seems to me also extremely probable that these processes, con- 
trary to Sagemehl’s statement (No. 102, p. 516), are the homo- 
logues of the pharyngeal process of Cyprinoids, and that these 
latter processes are thus also the homologues of the ventral 
arches of the tail. One reason given by Sagemehl for not so 
considering them is, that the pharyngeal process in Chondros- 
toma nasus is not performed in cartilage. This may be, in part, 
an error, as are certainly his statements that the intercalar in 
Amia is so performed, and that the prefrontal in Amia is in part 
a dermal bone. The other important reason given by him for 
