No. 468.) MUSCLES OF. ACANTHIAS AND RAIA. 913 
dibularis lateralis 22, it widens into a large muscle which dis- 
appears under the adductor mandibularis lateralis 2 to become 
inserted on the mandibular cartilage while a portion of its fibers 
become confused with the posterior portion of Ami 2 (Fig. 3). 
The third division (Fig. 6, Z/s 3) is thé smallest of the sys- 
tem: a short thick muscle running from the postero-lateral edge 
of the dorsal surface of the nasal capsule, laterally, to the poste- 
rior dorsal angle of the antorbital process, the fibers converging 
towards the insertion. 
The fourth division (Fig. 3, Lis 4) is broad, thin, and flat, 
and its origin is continuous with and ventral to that of the third 
division. It lies upon the adductor mandibularis lateralis and 
covers a portion of‘ it ventrally. The mandibularis branch of 
the fifth nerve runs between the two. Its general course is 
posterior and the fibers which are not inserted in the fascia 
covering the adductor mandibularis lateralis converge to a 
strong tendon, which makes its way through that muscle, to 
their insertion on the ventral surface of the mandible. 
The fifth division (Fig. 6, Z/s 5), though included by Tiesing 
among the muscles, is but a group of strong tendinous fibers 
having its origin just posterior to that of the second division 
and its insertion on the strong fascia enveloping that muscle. 
Muscular tissue is lacking in it, and it is scarcely more than à 
second origin of that muscle. 
Levator Rostri. 
This muscle (Fig. 6, Zr), together with the next, would be 
treated first among the superficial muscles were we describing 
Raia alone, but since it is lacking in Acanthias it has been left 
until now. Upon removing the skin from the dorsal surface, 
the levator rostri is the first seen and most superficial of the 
muscles. It takes its origin from the lateral edge of the lateral 
process of the first vertebra which projects above the surround- 
ing muscles, and from the tendinous fascia covering the muscles 
in this region. The fibers run obliquely forward, converging to 
the region where they cross the levator maxille superioris and 
the first dorsal constrictor where they pass into a strong cylin- 
