330 
EDWARD PHELPS ALLIS. 
alone, the vena jugularis here lying along the antero-ventral 
edge of the trapezius and partly internal to it. 
Each ventral extrabranchial turns posteriorly, at its ventral 
end, around the ventral edge of the next posterior gill-pouch 
immediately proximal to the lowest point of that curved 
edge., aud then spreads both anteriorly and posteriorly into 
long pointed processes. The posterior process hooks around 
the ventral edge of the next posterior gill-poucli and is 
prolonged, along the posterior surface of that pouch, by a 
line of fibrous tissue which lies in the line prolonged of the 
shank of the next posterior extrabranchial, and is inserted 
on that extrabranchial at the point where it bends pos- 
teriorly around the ventral edge of the gill-pouch next 
posterior to it. The anterior process of the extrabranchial 
of the first arch runs antero-mesially between the coraco- 
branchiales I and II, and nearly meets its fellow of the 
opposite side in the median line, being separated from it 
by the connective tissues that surround the truncus arte- 
riosus. The anterior process of the extrabranchial of the 
second arch is similarly related to the coracobranchiales II 
and III and to its fellow of the opposite side, while the 
anterior process of the extrabranchial of the third arch is 
similarly related to the coracobranchiales III and IV, but is 
separated from its fellow of the opposite side by a con- 
siderable interval because of the intervening ventral edge of 
the pericardial chamber. The antero-ventral ends of these 
anterior processes of the extrabrancliialis approach somewhat 
the inner branchial bars of their respective arches, especially 
in the first arch, but they are not especially attached to 
them by connective or ligamentous tissues. They do not 
turn posteriorly toward the inner branchial bar of the next 
posterior arch, and they are not connected with that bar by 
special ligamentous or connective tissues. 
The branchial constrictor that lies anterior to a given gill- 
pouch, and the related branchial and extrabranchial rays, 
are all quite strongly attached, by connective tissues, to the 
anterior wall of that pouch, but the constrictor of the arch 
