No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 653 
rounded by cartilage excepting’ in that portion that lies between 
the points where the element articulates with the second and 
third epibranchials. This exposed bony edge thus corresponds 
to the distal half of the anterior edge of the second infra- 
pharyngobranchial. At about the middle of the postero-lateral 
edge of the element there is a slight thickening on its dorsal 
surface marking the point where it articulates with the fourth 
epibranchial. In front of and behind this thickening, near the 
edge of the piece, there are one or two perforations for the 
passage of pharyngeal branches of the vagus. 
The fourth epibranchial (£4./1V’) is a flat piece, not grooved 
on its dorsal surface, and about as long as the second epi- 
branchial. It is capped at both ends with cartilage, the proxi- 
mal cap having three strong processes, an anterior, a median, 
and a posterior, the two latter passing beyond the outer edge 
of the third infrapharyngobranchial dorsal to that piece. By 
the anterior process it articulates with the third epibranchial, 
and by the posterior with the third infrapharyngobranchial, the 
attachment to the latter piece being very strong, the ligament 
passing between the two pieces and forming there a tough pad 
of tissue. The piece is considered by van Wijhe as the fourth 
infrapharyngobranchial because of the articulation in front with 
the third epibranchial; but as it articulates also, and much 
more strongly, with the posterior portion of the large and per- 
haps compound third infrapharyngobranchial, there is equally 
good reason for considering it as an epibranchial. Between 
the posterior articulation, with the third infrapharyngobranchial, 
behind, the two articulations at the proximal end of the third 
epibranchial in front, the third infrapharyngobranchial below, 
and the fourth epibranchial above, there is a large open passage, 
but no vessel or structure of any apparent importance was found 
passing through it. 
The fifth epibranchial (H4.V) has been described with the 
ceratobranchial of its arch. 
c. Hyoid Arch. 
The hyoid arch, as ordinarily considered, consists of three 
parts. These three parts are, in Amia, the hypohyal, the 
