550 
CAPTAIN E. W. SHANN ON 
anterior border of the scapula, and its fibres, passing forwards and slightly down- 
wards, take origin on the posterior aspect of the strong post-orbital ridge of the 
cranium ; to this muscle the name protractor dorsalis pectoralis is given. 
The p.d.p. is covered to a certain extent by the l.p. ; this is particularly marked 
in Callorhynchus, where a tract of the latter muscle is excised in the drawing in 
order to expose the insertion of the former. 
(b) Muscles derived from the mesio-ventral portion of the lateral muscle. 
(i) Levator pectoralis (l.p.). Trapezius superficialis, Vetter; Trapezius, 
Jaquet. 
Arising from the post-orbital ridge of the cranium, opposite to the lower half of 
the orbit in Chimsera, opposite the entire orbit and extending above its level in 
Callorhynchus, the fibres of this muscle run backwards and downwards to their 
insertion on the outer aspect of the scapula. The insertion extends in an arc in 
Chimsera, while in Callorhynchus it runs in a straight line, parallel with that of r.l.v.p. 
The similarity of the insertion levels of the muscle under consideration and of the 
r.l.v.p., and the similar direction taken by their fibres, led me at first to believe 
that the former was also a derivative, of the latero-ventral portion of the lateral 
muscle — in fact, that it represented the p.l.v.p. of Selachians. The origin of the 
muscle high up upon the cranium seemed also to agree with such a conclusion. 
Vetter’s observation that this muscle in Chimsera is innervated in a precisely 
similar manner to the “trapezius” [i.e. levator pectoralis) of Acanthias, namely, by 
certain twigs from the ramus intestinalis of the vagus, seems to me a weightier 
argument than one based on mere topographical grounds. Moreover, there is a 
small muscle, figured and described by Vetter as trapezius profundus, which lies 
beneath the foregoing mass. The origins of these muscles are conterminous, they 
run parallel to one another, but whereas the larger outer one is inserted upon the 
scapula, the smaller inner one is inserted upon the last pharyngo-branchial. Now, 
this last recalls the small muscle which was mentioned under the Selachii (see p. 540)- 
as a part of the so-called trapezius. It appears, then, that the protractor latero- 
ventralis pectoralis is entirely wanting in Holocephali. 
(ii) Coraco-branchiales (c.br.). Coraco-branchiales, Vetter, Jaquet. 
A muscular sheet of uniform thickness, arising from the anterior border of the 
girdle (both scapular and coracoid portions), is inserted by very short branches on 
the lowermost portions of the gill arches, thus indicating its composite structure. 
From the nature of their insertions it follows that the fibres are short dorsally and 
increase in length as the ventral border of the muscle is approached. The muscle 
serves, as in the Selachians, to form the lateral wall of the pericardium. 
Vetter has described this muscle in considerable detail for Chimsera (88, 
Taf. xii, fig. 5). 
The general relations of the muscle are similar in Callorhynchus. 
