MANDIBULAR AND PHARYNGEAL MUSCLES OF 
ACANTHIAS AND RAIA! 
GUY ELLWOOD MARION. 
INTRODUCTION. 
THE following paper deals only with the muscles of the jaw 
and branchial region in the common dogfish (Acanthias vulgaris), 
and in one of the common skates (Raza erinacea). The existing 
literature upon this subject is very scanty, and aside from a 
few scattered references to the muscles, I have found only the 
detailed papers by Vetter (74) upon the mandibular and bran- 
‚chial regions of the sharks, and a similar paper by Tiesing ('95) 
who discusses in the same way the muscles of the skates. 
Drüner (:03) uses the Selachians in describing the visceral mus- 
cles of the Urodeles. 
The present article follows very closely the work of Vetter 
and Tiesing, especially that of the former.  Tiesing classifies 
and arranges the muscles upon the basis of innervation; Vetter 
upon that of position and function. That the former method 
has its advantages is admitted, but convenience leads me to 
adopt the scheme of Vetter; and although not agreeing with 
him in all points, I have adopted as far as possible his nomen- 
clature and lettering of the figures. As was said above, Vetter 
deals only with the sharks, and Tiesing with the skates, while 
I have tried to draw homologies between the two groups, and 
this has led me at times to differ from my predecessors. 
The mandibular and branchial muscles may be divided into 
four main groups : — 
1. Superficial circular muscles. 
2. Interarcuales (muscles between the upper ends of the 
branchial arches). 
3. Adductores (flexors at the middle of the arches). 
1 Contributions from the Biological Laboratories of Tufts College, No. XLIII. 
891 
