No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 735 
fused with the hind end of the skull to form the postauditory 
or occipital region. In larvae but four such vertebrae are in- 
dicated. -Whether the dorsal arches may have shifted from the 
anterior end to the posterior end of their respective vertebrae, 
or not, makes no difference in the count. If, however, the 
last occipital arch of the adult is to be assigned to the first 
vertebra, the count would be diminished by one. The septa 
seem to preclude such a supposition. 
5. Review and Comparison. 
In comparing the occipital region in Amia with that in other 
animals, some fixed point must first be found. The anterior 
end of the first muscle segment seems to be such a point ; but 
there may have been still other, more anterior, muscle segments 
that have disappeared, as there certainly is one nerve that has 
disappeared, that of the first existing muscle segment. Another 
point that would seem to be fixed, and wholly independent of 
the possible disappearance of such segments, is the fifth inter- 
muscular septum. This septum seems to mark, in both fishes 
and reptiles, the posterior limit of the muscle segments, or 
myotomes, from which the muscles of the tongue primarily 
develop; and the anterior limit, in fishes, of the segments that 
enter into the formation of the muscles of the pectoral fin. 
In Scyllium and Pristiurus the coraco-hyoideus, or sterno- 
hyoideus, develops, according to van Wijhe (No. 130, p. 16), 
from ventral prolongations of the last three head myotomes 
and the first trunk myotome. Corning (No. 21), in Scyllium, 
assigns the same posterior limit to the myotomes so concerned, 
but adds the first head myotome to the number. In teleosts, 
also, Corning finds the “‘ Hypoglossusmusculatur”’ arising from 
the first five myotomes, confirming in this Harrison’s earlier ob- 
servation (quoted by Corning). In reptiles both he and Mollier 
(No. 82) find the muscles of the tongue arising from the first 
five myotomes, but Corning states that in late stages these 
muscles receive additions from the sixth and seventh myotomes. 
In Acanthias the coraco-hyoideus develops, according to Hoff- 
mann (No. 57, p. 639), from the fourth occipital myotome, that 
