920 THE AMERICAN NATURALIST. |. [Vor. XXXIX. 
VENTRAL LONGITUDINAL MUSCLES. 
The location and character of these muscles is apparent from 
this name. In Acanthias they are usually thick and solid, while, 
correlated with the depressed body, they are flat and thin in 
Raia. 
Coraco-mandibularis. 
Acanthias. 
In the dogfish the coraco-mandibularis is an azygos muscle 
lying in the median line of the body, and is exposed (Fig. 5, Cmm) 
by removing the ventral constrictors. It is the most superficial 
of the ventral longitudinal muscles. It arises from the fascia 
between the coraco-arcuales communes and its fibers rapidly 
diverge near the origin, where the muscle is nearly circular in 
section, to form a flattened band which is inserted on the poste- 
rior edge of the lower jaw on either side of the symphysis. 
Raia. 
In the skate the coraco-mandibularis (Figs. 3, 15, Cm) also lies 
in the median line but is not covered by the ventral constrictors, 
since these are here more lateral in position, with the exception 
of a few fibers (Fig. 3, Csv 7) already described. In origin and 
insertion there is a close agreement with Acanthias, but the mus- 
cle is thinner and flatter than in that form. With the exception 
of the depressor rostri and the depressor mandibuli, whose ori- 
gins overlap its margin, it is the most superficial of all the ven- 
tral muscles. 
Coraco-hyoideus. 
De Acanthias. 
The coraco-hyoideus muscles (Fig. 4, Chy) are exposed by 
removing the coraco-mandibularis, which lies close to the me- 
dian line. They are the largest of the ventral longitudinals. 
