620 EDWARD PHELPS ALLIS, JR. 
are quite certainly represented in the suprapharyngobranchials 
of van Wijhe’s descriptions of ganoids and Polypterus and the 
ventral ones in processes of certain of the hypobranchials of cer- 
tain of those same fishes. The suprapharyngobranchials may 
be found as independent cartilages, or they may be found fused 
with the pharyngobranchial or epibranchial of their respective . 
arches and so appearing as processes of those elements. 
Interarcual cartilages, developed in or in relation to the dorsal 
interarcual ligaments and corresponding in position to the epi- 
tremal longitudinal. branchial bars of the Cyclostomata, are 
found in many of the Plagiostomi, and, like the suprapharyngo- 
branchials, they may be found either as independent cartilages 
or fused with the adjacent elements of the inner cartilaginous 
bars. Similar cartilages are apparently also found in Scomber 
and Ceratodus. 
In the Selachii the hyomandibula is formed by the epihyal, 
in the Batoidei by the pharyngohyal, and in all these fishes the 
hyomandibula always articulates with the neurocranium ventral 
to the vena jugularis. In what is apparently definite correlation 
to this, the dorsal extrabranchial of the hyal arch persists, as an 
independent cartilage, in most if not in all these fishes. The 
interarcual cartilage that lies between the mandibular and hyal 
arches may be wholly wanting, may apparently be found as an 
independent cartilage (Narcine), or found fused with the ante- 
rior edge of the hyomandibula (Torpedo) and appearing as a proc- 
ess of that element. = 
In the Holostei and Teleostei the hyomandibula always ar- 
ticulates with the neurocranium dorsal to the vena jugularis, 
and hence is in protective relations to that vein; and quite cer- 
tainly in definite correlation to this, there is no independent ex- * 
trabranchial cartilage in the hyal arch and no superior post- 
spiracular ligament or its related interarcual cartilage. These 
two cartilages, the extrabranchial and interarcual, are accord- 
ingly, in all probability, respectively represented.in the posterior 
and anterior articular heads of the hyomandibula of these fishes. 
The interhyal is the epal element of the arch. The symplectic 
is probably a primarily independent cartilage, and is possibly a 
