386 
EDWARD PHELPS ALLIS. 
myotome and not from a part of the cephalic coelom, as above 
explained, then the musculus intermandibularis must be 
developed from a corresponding portion of the mandibular 
myotome, for Edgeworth says (loc. cit., p. 226) that these two 
muscles are serially homologous. This conclusion is inevitable 
if the premises are correct, and the intermandibularis, although 
lying actually, in sections, ventral to the interhyoideus, would 
lie morphologically entirely in front of that muscle. This 
Text-fig. 1. 
explanation of Edgeworth's observations would also establish 
that the intermandibularis and interhyoideus of his descrip- 
tions could not be the coracobranchialis + coracomandibularis 
of van Wijhe's (1882 b) earlier descriptions, notwithstanding 
the marked similarity in the descriptions of their derivation. 
Of fishes other than tlie Selachii Edge worth says (loc. cit., 
p. 209) that, in 8 mm. embryos of Acipenser, the hyal 
muscles “ consist of a hyoid myotome, the anterior part of 
which is inserted into the upper end of the hyoid bar, forming 
a levator hyoidei, and the posterior part of which forms a 
dorso-ventral sheet — homologous with C 2 vd of selachians — 
