918 : THE AMERICAN NATURALIST. (Voi: XXXIX. 
The second division of the levator labialis superior, in its 
course to its insertion on the ventral surface of the lower jaw, 
crowds into the superficial layer of the lateral mandibular adduc- 
tor, separating it in part into anterior and posterior portions. 
The anterior of these divisions (Am/ 2a) arises in part from the 
dorsal surface of the lower jaw, directly opposite to its point of 
attachment to the deeper layer, and in part from the ventral 

Fic. 13.— Lateral view of adductor mandibularis of Acanthias. Am, adductor mandibularis ; 
Csv ra, constrictor superioris ventralis, anterior fibers; y, tendinous mass back of eye. 
surface by means of a very strong fibrous tendon. It runs for- 
ward, passing dorsally to the upper jaw and immediately broad- 
ens out into a large mass of fibers which curve ventrally and run 
backward, covering the deeper layer of the adductor and finally 
becomes inserted upon an aponeurosis surrounding the deeper 
layer. From this aponeurosis the fibers start again and continue 
backward, completely encasing the ends of both jaws, to the 
insertion directly and by means of tendons upon the lower jaw. 
Adductores Arcus Branchialis. 
The hyomandibular and hyoid cartilages are bound together 
at their articulation by strong ligaments, but no adductors are 
present connecting the two. In the branchial arches proper 
such muscles occur. 
