650 ALLIS. (Vou. XII. 
higher level than the anterior one, and its ventral surface 
deeply grooved through its entire length. Both ends of the 
piece are capped with cartilage, the cap on its outer, distal end 
curving downward and diminishing gradually in thickness 
toward the end, where it meets and is bound to the upturned 
cartilaginous end of the ceratobranchial of its arch, a space 
being thus left in the angle between the two pieces. The cap 
on the inner, proximal end of the piece extends backward a little 
along the posterior edge of the piece, and has on the distal end 
of this part, just before it unites with the bone, a slight em1- 
nence, which in one specimen had on its summit a small tit-like 
process. The cartilage along the middle portion of the cap 
seems sometimes to be wanting, thus leaving two separate caps 
on the proximal end of the piece. 
The posterior, upper corner of the proximal end of the 
first epibranchial articulates with the infrapharyngobranchial 
(JPB.L1) of the next following, or second arch, at about the 
middle of its anterior, upper edge, the articulation being with a 
prolongation of the cartilaginous proximal cap of that element. 
The ligamentous articular attachment of the two elements, 
however, extends outward, that is, distally, for a short distance 
along the anterior edge of the bony portion of the infrapha- 
ryngobranchial, and is continuous both at its origin and inser- 
tion with the ligamentum interarculae dorsale of the first arch. 
This ligament (/zd./) arises from the posterior edge of the 
proximal cartilaginous cap of the first epibranchial, and is 
inserted along the anterior edge of the second infrapharyngo- 
branchial, from the middle of its length to the outer end of the 
piece, the insertion even passing slightly onto the adjacent 
proximal end of the second epibranchial. Between the two 
ligaments, or more properly through the continuous united liga- 
ments, there is a sharply defined circular aperture for the pas- 
sage of the pharyngeal branch of the first vagus nerve. 
The anterior and lower corner of the proximal end of the 
first epibranchial articulates with the infrapharyngobranchial 
of its arch. This latter element (/P8./) is a long slender bone 
capped at each end with cartilage and slightly grooved on its 
posterior or postero-dorsal surface, the groove turning forward 
