'HE SHOULDER GIRDLE AND PECTORAL FIN OF FISHES. 
533 
Key to the Musculature of the Pectoral Arch and Fin in Elasmobranohii. 
Gegenbaur. 
Humphry. 
Marion. 
Owen. 
WlEDERS- 
HEIM. 
Vetter. 
Remarks. 
(a) Retr. lat.-dors. pect. 
Not always present. 
(6) R. lat.-vent. pect. . 
Lat.-scapul. 
Serratus. 
Neuro-lat. 
Serratus of Braus. 
Posterior 
M. du ventre of 
fixation 
(c) R. mes.-vent. pect. 
muscles. 
(i) Superior 
Latiss. dors. 
Jaquet. 
(ii) Medius . 
Axili. por- 
tion. 
(iii) Inferior 
Pectoralis. 
' (a) Protr. lat.-dors. pect. 
Not always present. 
(6) P. lat.-vent. pect. *. 
Protr. scap. 
Wanting in Holo- 
Trapezius 
cephali. 
Trapezius of 
(c) Mesio-vent. derivs. . 
(pars). 
Jaquet. 
(i) Levator pect. 
Trapez. 
Levator scap. 
Trapez. 
Anterior 
(pars). 
(pars). 
fixation 
(ii) Coraco-arc. comm. 
Cervic. prof. 
Coraco-arc. 
muscles. 
(pars). 
comm. 
Coraco- 
(iii) Coraco-brancli. 
Deepest part 
Coraco- 
Coraco- 
of c.p. 
brancb. 
branch. 
branch. 
(iv) Coraco-hyoideus . 
Cervic. prof. 
Coraco- 
Coraco- 
Coraco- 
(pars). 
hyoid. 
hyoid. 
hyoid. 
(v) Coraco-hyomandib. 
Coraco- 
hyomandib. 
Only in Raia. 
(vi) Coraco-mandib. . 
Coraco- 
Depressor- 
Coraco- 
Coraco- 
mandib. 
mandib. 
mandib. 
mandib. 
• (a) Adductor. 
(i) Superficialis. 
Fin 
(ii) Profundus. 
muscles. " 
(6) Abductor. 
(i) Superficialis. 
(ii) Profundus. 
I. Selachii. 
(Scyllium canicula, Galeus canis, Acanthias vulgaris , Rhina squatina, 
Raia clavata.) 
1. Shoulder Girdle. 
(l) The Lateral Muscle. 
Throughout its length the lateral muscle of Selachians is divided into a dorsal and 
a ventral moiety by a horizontal septum running from the lateral line to the trans- 
verse processes, and, further back, to their equivalents, the haemal arches. In the 
dorsal moiety of the tail region (text-fig. l) the myocommata may be traced super- 
ficially from the mid-dorsal line, running first forwards, then sharply backwards, then 
gently forwards again ; following the same myocommata through the ventral moiety, 
they are seen to run first backwards, then gently forwards, lastly sharply backwards. 
On examining a transverse section of the tail, it is seen that the myomeres enclosed 
