126 Cc. H. DANFORTH 
such be the case it is difficult to see how, on the one hand, in 
Polyodon and apparently Amia the innervation of the muscle 
has been changed, or on the other hand, if the same fibers still 
supply it, how they have crossed over the cartilage so as to 
approach the muscle from the other side. A further comparative 
study on this group of muscles seems very desirable. 
MM. interarcuales ventrales 
The four ventral interarcuate muscles seem to be identical in 
all respects with the similar muscles in Acipenser. In the follow- 
ing brief account of each, I have described them in the reverse 
order, as compared with Vetter’s account of Acipenser, i.e:, from 
a physiological rather than a morphological standpoint. 
1. The most anterior arises by a short tendon of origin from 
the hypohyal, a little lateral to the insertion of the coraco-arcualis 
tendon. It is inserted on the cerato-branchial I for a short 
distance along its ventral margin and on its anterior face close 
to the margin. It differs from the following muscles in that it 
extends between two different arches, the hyoid and the first 
branchial. 
2. The second is a short muscle filling the small triangle 
between the hypo- and cerato-branchial cartilages of the second 
arch, ventral to their articulation with each other. 
3. The third has relationships in the third arch similar to those 
of the second in its arch. Some of its fibers, however, may be 
inserted on the posterior as well as the anterior face of the cerato- 
branchial near its ventro-mesial margin. It is in this respect 
somewhat transitional between the fourth and those anterior to 
it. 
4. The most posterior is the only one of these muscles that 
arises from a basibranchial cartilage. It has its origin from the 
third basibranchial cartilage, close to the articulation of the 
fourth branchial cartilage, and is inserted on the ventro-medial 
margin and posterior face of the latter. 
Innervation. Each of these muscles is supplied by the same 
nerve plexus that supplies the corresponding adductor arcuus 
branchialis. 
