900 THE AMERICAN NATURALIST. | [Vor. XXXIX. 
margin to the first constrictor. In front the fibers of this 
muscle are not separated by a median aponeurosis, but run from 
one half of the jaw to the other. 
Like the second dorsal, the second ventral constrictor (Fig. 5, 
Csv 2) is much the largest of the series. It does not extend as 
far forward as Csv 7, but, on the other hand, it extends back to 
the first gill cleft. About half of its fibers arise from the me- 
dian aponeurosis, run parallel with those of the first ventral con- 
strictor, and are inserted on the ventral edge of the ceratohyal 
cartilage. The posterior fibers, on the other hand, have their 
origin in the aponeurosis separating the second and third ventral 
constrictors, and, as they become too posterior to find attach- 
ment to the lower jaw or to the ceratohyal, they are inserted 
upon the fibrous bridge mentioned in connection with the sec- 
ond dorsal constrictor (p. 895), while still farther back the fibers 
run over into those of the first dorsal constrictor, passing in 
front of the first gill slit and running parallel to its margin. 
The remaining ventral constrictors (Csv 3-Csv 6) are closely 
similar to each other, the only difference being in the points of 
origin. Excepting 3 and 6, the origin is either in the aponeu- 
rosis between each and the next succeeding muscle, or, in the 
case of the median fibers, from the fascia between the gill cavi- 
ties and the common coracoid muscles. The most medial fibers 
of the second muscle take their origin, like those of Csv 2, in the 
median line ventral to the common coracoids, while the sixth has 
its origin in the pectoral girdle and in the fascia covering the 
ventral fin-muscles. The fibers of all of these muscles are 
either inserted in the aponeurosis in front, or are continued 
dorsally and laterally over into the dorsal constrictors. 
The function of the constrictors is to compress the pharyngeal 
chamber, eject the water, and close the gill slits. The first dor- 
sal constrictor may assist in raising the upper jaw, and the sec- 
ond may raise the hyoid arch, while the first and second ventral 
constrictors lower the under jaw and the hyoid respectively, thus 
assisting in the opening of the mouth. 
