No. 468.] MUSCLES OF ACANTHIAS AND RAIA. 895 
zum Faserverlauf dieser Partie nach aussen gerichtet sind, lagern 
sich dabei ihrer hintern Fláche dicht an, so dass diese zu den 
Spritzlochknorpeln genau in dieselber Beziehung tritt, wie sie 
zwischen den Mm. interbranch. und den knorpeligen Radien 
des Kiemenbogen, oder zwischen Cs4 2 und Csv 2 und den Radien 
des Zungenbeinbogen besteht.” 
Vetter has not carried his comparisons far enough. If these 
fibers nearest the spiracular cartilages bear the same relation to 
these cartilages as do those of the second dorsal and ventral 
constrictors to the rays of the hyoid arch, then why do they not 
represent another constrictor muscle Csd 7 exactly like Csd 2 in 
general relations? By a further comparison with Raia (Fig. 6) 
we see that the general course of the fibers of the posterior part 
as well as the insertion make this part distinctly comparable to | 
the Csd 7 of that form. 
The second dorsal constrictor (Fig. 2, Csd 2) is by far the 
largest of the dorsal constrictors. It is a wide flat muscle 
extending from just behind the spiracle to the first gill slit. In 
front it arises from the postero-lateral surface of the cranium, 
farther back from the strongly fibrous fascia which completely 
covers the dorsal muscles. This origin extends as far back as 
the anterior end of the trapezius (Fig. 11) and even beyond that 
the fibers send tendinous attachments through the trapezius to 
their origin in the main tendinous fascia covering the longitudi- 
nal muscles. The first dorsal aponeurosis between the constric- 
tors runs from the point where the fibers enter the trapezius in 
an obliquely ventral direction to the dorsal end of the first gill 
cleft. From this aponeurosis the more posterior fibers of (sd 2 
take their origin. The fibers of the muscles run obliquely from 
their origin on the dorsal margin of the muscle. 
The insertion is also diverse. The most anterior fibers, which 
bound the spiracle behind, are inserted at the quadrate end of 
the upper jaw. The next fibers run around and cover the hyo- 
mandibula and are inserted upon the ceratohyal cartilage. This 
portion of the muscle corresponds to the levator hyomandibularis 
of Raia, where, attached to the same visceral arch, it has become 
much further developed. Beyond this portion the fibers are 
inserted upon a tendinous bridge connecting the dorsal and ven- 
