No. 468) MUSCLES OF ACANTHIAS AND RATA. 92I 
The origin of each is very long, extending along the fibrous 
aponeurosis between it and the coraco-branchialis and the cor- 
aco-arcualis communis, from beneath the origin of the coraco- 
mandibularis halfway to its insertion on the ventral side of 
the hyoid copula just behind the lower jaw. The muscle is as 
thick as broad and only diminishes slightly in size in front. 
Rata. 
In the skate the coraco-hyoideus muscles (Fig. 3, Chy) are 
reduced, flat, and thin. Each arises from the fascia covering 
the large coraco-hyomandibularis, near the origin of the second 
interbranchial muscle and is inserted upon the ventral surface 
of the hypohyal cartilage. It lies deeper than the depressor ros- 
tri, the depressor mandibularis, and the depressor hyomandib- 
ularis, and directly upon the coraco-hyomandibularis. 
Coraco-branchialis. 
Acanthtas. 
The coraco-branchialis (Figs. 4, 10, Cér) is the deepest and 
most dorsal of the ventral longitudinal muscles and forms the 
lateral wall of the pericardial cavity. It is composed of five 
parts, of which the last four have a common origin. The first 
division (Cér 7) arises from an aponeurosis directly beneath the 
coraco-hyoideus, and running dorsally becomes inserted on the 
dorsal surface of the medial end of the hyal cartilage. It is 
much shorter than the ceratohyoid and is contracted near its 
insertion. : i 
The four remaining coraco-branchials (Fig. 10, Cbr 2-4) arise 
from a strong membrane running from the girdle to the origin of 
the ceratohyoid. As the fibers pass forward and laterally they 
divide into separate portions, the anterior of which becomes 
inserted on the branchial arches, while the last, which is much 
the largest, is inserted upon the fifth arch and upon the lateral 
half of the copula. Blood vessels pass through the arches 
between the divisions of the muscle. 
