33 FISHES OF SINALOA. 405 
On the upper part of the operculum is a large scale- 
like bone. 
The suborbitals are well developed and plate-like, ex- 
tending back nearly to the posterior edge of the preopercle. 
6. Vertebral Column. 
There are forty-two vertebre in the spinal column. 
The first vertebra is co-ossified to the skull, and appar- 
ently bears no ribs; the second vertebra supports a pair 
of very small, slender ribs, which articulate directly with 
the sides of the vertebra; the third vertebra supports the 
first pair of large ribs; they are articulated with the trans- 
verse processes. 
The first fourteen or fifteen neural spines and pairs of 
transverse processes are articulated with the vertebra by 
sutures, they are easily separated from the vertebra by 
boiling or maceration. 
The vertebre gradually increase in size and reach their 
largest size about two-thirds of the distance from the an- 
terior to the posterior end of the spinal column, where 
they are three or four times the size of the anterior ones. 
This character is more marked in the adult than in the 
young. 
c. Shoulder Girdle. 
The shoulder girdle is exceedingly well braced, the 
post-temporal is widely forked, and strongly articulated 
to the epiotic processes of the skull. 
The supra-clavicle is long and slender, its posterior face 
is hollowed out and attached some distance from the upper 
end of the clavicle, which projects upward. 
This projecting upper end of the clavicle is braced to 
the skull by two long bones.* The first bone is very 
slender, at its anterior end it is connected to the exocci- 

*See Dr. R. W. Shufeldt’s report on the osteology of Amia calva; Bull. 
U.S. F. C., 1883, page 59. 
