No. 3.] WUSCLES AND NERVES IN AMIA CALVA. 649 
also slightly onto the edge of the bone immediately beyond 
the cap. This interarcual attachment, on this arch, is stronger 
even than that of the ceratobranchial to the basal line. 
The ceratobranchials (CB./-/V) of the first four arches are 
semi-cylindrical pieces, slightly curved upward and deeply 
grooved on their ventral surfaces. They are thicker at their 
inner, or distal, than at their outer or proximal ends, this being 
especially marked in the third and fourth arches, and they are 
capped at both ends with cartilage. The distal cartilaginous 
caps have each a prominent swelling on the anterior half of 
their ventral surface, and beyond, that is distal to, the swell- 
ing, the ventral edge of the cartilage is bevelled, so that the 
articulation with the hypobranchial lies at a higher level than 
the ventral surface of the piece, thus leaving a hollow for the 
reception of the outer ends of the muscle of the arch. The 
proximal cartilaginous caps bend slightly upward, and that of 
the fourth arch has on its posterior edge a large, flat, thin pro- 
jection, giving to the cap a triangular shape. The ceratobran- 
chial of each arch is bound to its hypobranchial by strong liga- 
mentous or connective tissue, which passes in between the two 
pieces and forms a tough, relatively thick, bi-concave pad be- 
tween them. 
The ceratobranchial of the fifth arch (CB.V) is shorter and 
more slender than those of the other arches, is only faintly, or 
not at all grooved on its ventral surface, and is triangular in 
section. The cartilaginous cap at its distal end is relatively 
large and flat, that at its proximal end much like those on the 
other arches. Attached to the extreme posterior and outer 
corner of the proximal cap is a small piece of cartilage (EB.V), 
already referred to, which represents either the epibranchial or 
one of the pharyngobranchials of the arch. Because of its rela- 
tion to the ceratobranchial I have considered it as an epibran- 
chial, although in its relation to the muscle of the arch it 
strikingly resembles the suprapharyngobranchial of the second 
arch. 
The epibranchial of the first arch (Z4./) is triangular in 
shape, the base of the triangle directed inward and forward, 
that is, proximally, with its posterior corner lying at a much 
