318 
EDWAllL) PHEU'S AELIS. 
distal (posterior) fibres of the dorsal part of each constrictor, 
misleadingly called by Vetter the “ untersten ” and by Marion 
the “ ventral” ones, are said by both those authors to traverse 
the branchial diaphragm and to be continuous with the cor- 
responding fibres of the so-called ventral portion of the 
muscle. 
The distal and larger part of the fibres of the ventral por- 
tion of the constrictor of each arch are said to have their 
origins on the linear aponeurosis that extends ventro-anteriorly 
from the ventral end of the next posterior gill opening. In 
the first branchial arch, the remaining, proximal fibres of the 
constrictor, here called by Vetter the “ untersten/’ and by 
Marion the {! median ” fibres, are said to have their origins in 
the mid-ventral line from the tendinous ventral surface of 
the hypobrancliial muscles, and the corresponding fibres in the 
second to the fourth arches to have their origins from a so- 
called aponeurosis related to a fascia that lies dorsal to the 
hypobranchial muscles and serves as surface of origin for 
them. Running antero-dorsally, the proximal (anterior) and 
larger portion of the fibres of each constrictor, including the 
little proximal bundles above referred to, are all inserted on 
the next anterior linear aponeurosis, while the remaining, 
distal (posterior) fibres turn dorsally and are continuous with 
the corresponding fibres of the dorsal portion of the muscle. 
Excepting only the little bundle of proximal fibres in the 
first branchial arch, the ventral ends of the constrictores 
superfieiales of this fish thus only reach the dorsal or dorso- 
lateral edge of the hypobranchial muscles, and comparison 
with Heptanchus led Vetter to conclude that the ventral ends 
of the constrictores of Acanthias had undergone marked 
reduction. He calls especial attention to this, and says (loc. 
cit., p. 441) that the disappearance of these ventral portions 
of the constrictores of Acanthias is related to the great develop- 
ment of the hypobranchial muscles, but he makes no mention 
of what would seem to be a strictly similar disappearance of 
the larger part of the corresponding dorsal fibres. This 
assumed disappearance in Acanthias, and also in Scymnus, of 
