394 
ED W Alii) PHELPS ALLIS. 
and the embryological evidence are, however, both against 
this supposition. 
Edgeworth (1911) derives both the levator labii superioris 
of the Plagiostomi and the four divisions of the levator 
maxillae superioris of my descriptions of Amia, directly from 
the adductor mandibulae, and from that portion only of the 
primitive mandibular constrictor. Luther also derives these 
four muscles of Amia directly from the adductor mandibulae ; 
and he proposes for the first and second divisions of the 
muscle the name musculus adductor mandibulae parabasalis, 
because of their partial origin from the lateral wing of the 
parasphenoid (parabasalis, Gaupp), and for the third and 
fourth divisions of the muscle the names musculus adductor 
mandibulae praeorbitalis and musculus nasalis. Edgeworth 
considers the muscles of Amia to all be upgrowths of the 
internal and deeper portion, only, of the adductor of the 
adult, and suggests that they be named in terms of that 
internal adductor. The myotome of this arch is, according 
to him, definitely and entirely cut into dorsal and ventral 
portions where it crosses the dorsal edge of the palatoquadrate; 
these two parts remaining always distinct and separate, while 
the intermandibularis is, as already stated, developed wholly 
from the walls of the cephalic coelom. Until the derivation 
of these muscles is definitely known it would seem best not to 
give them names based wholly or largely upon it. 
There remains now only the aponeurotic septum of the 
adductor mandibulae to be considered. Fiirbringer (1903, 
p. 383), considered this aponeurosis to be of secondary origin 
and of no great morphological significance, it being developed, 
in fishes where the mouth opening had a pronounced posterior 
extension, simply in order to give space for suitable develop- 
ment of the belly of the adductor. Luther . (1909, p. 61) 
thinks this an insufficient reason for the development of the 
aponeurosis, and considers it to have been secondarily 
developed, after the development of the levator labii superi- 
ors (praeorbitalis), in order to furnish an attachment for that 
muscle on the quadrato-mandibular joint, and so facilitate its 
