No. 3:] “USCLES AND NERVES [N AMIA CALVA, 7it1 
arising from the posterior end of the basioccipital, and, like 
them and like the ribs, lying in an intermuscular septum. 
The ventral cartilaginous process on each vertebra is small, 
is round or oval, arises slightly beneath the surface of the 
vertebra, and projects but slightly beyond that surface. The 
dorsal process is much larger and much more important than 
the ventral one. It arises, like the ventral one, slightly beneath 
the surface of the vertebra, but it projects, at its median edge, 
considerably above that surface. It extends longitudinally 
across the dorsal surface of the vertebra, and is wedge-shaped, 
the edge of the wedge lying transversely, as do the edges of 
the wedge-shaped projections on the dorsal surface of the basi- 
occipital. The posterior face of each process is intimately 
united with a dorsal spinal arch (DA), so intimately, in fact, 
that the two form a single piece and cannot be separated with- 
out fracture. A surface line, however, indicates a plane of 
separation between them. 
The first six spinal arches, the only ones examined, are wedge- 
shaped at their lower ends, and fit in between the wedge-shaped 
dorsal processes of two adjoining vertebrae. They are there- 
fore, in position, strictly intervertebral, as Franque described 
them (quoted and contradicted by Schmidt, No. 110, p. 751). 
They are capped above and below with cartilage, and on the 
median side of the ventral end of each there is an indentation 
which extends entirely through the cartilaginous cap of the 
piece, and, on the sixth arch, slightly into the bone itself. On 
the sixth arch the indentation or groove extends from the 
median face of the arch almost to its lateral surface. The 
cartilaginous cap on this arch thus had the appearance of two 
oval pieces placed transversely, and connected, at their lateral 
edges, by a narrow strip of cartilage. Whether this is an 
indication that the arches are double in origin, as Goette (No. 
49) finds them in reptiles, or not, I am unable to state. 
Nothing else in their development, in Amia, from 12 mm. 
larvae upwards, indicates such a double origin. The inden- 
tation on all the arches is filled with ligamentous tissue con- 
nected with, and doubtless derived from, the ligamentum longi- 
tudinale dorsale inferior. The anterior face of the cartilaginous 
