578 EDWARD PHELPS ALLIS, JR. 
times been made were found developed in, or in relation to, 
the series of dorsal interarcual ligaments which extend from one 
branchial arch to the next, at or near the points where the pharyn- 
gobranchials and epibranchials articulate with each other. 
In the one specimen of Chlamydoselachus examined there 
were none of these cartilages excepting only the one already re- 
ferred to which lies in the ligament that extends from the hyal 
to the first branchial arch. 
In one specimen of Torpedo ocellata there was an interarcual 
cartilage related to each of the interarcual ligaments, and there 
was also one in a ligament which extends from the first branchial 
arch to the ventral portion of the hind end of the neurocranium; 
this last ligament evidently being the one that primarily extended 
from the first branchial to the hyal arch. 
In one specimen of Raia radiata there was, on one side of the 
head, aninterarcual cartilage related to the ligament which extends 
from the first to the second branchial arch, this cartilage lying 
close against the hind edges of the pharyngobranchial and epi- 
branchial of the first arch. On the other side of the head a pro- 
cess on the hind edge of the first pharyngobranchial corresponded 
exactly, in position, to the independent cartilage on the other 
side, and similar processes were found, on both sides of the head, 
on the pharyngobranchials of the more posterior arches. These 
processes thus apparently represent a series of interarcual carti- 
lages that have each fused with the pharyngobranchial of the 
next anterior arch. On one side of the head of this specimen a 
small and independent bit of cartilage was found at the dorsal 
end of the epihyal, apparently representing the dorsal interar- 
cual that lies between the hyal and first branchial arches. Simi- 
lar cartilages are said by Gegenbaur (’72, p. 175) to be found in 
most of the Batoidei, and he considered each of them to repre- 
sent a pharyngohyal that had been segmented off from the dor- 
sal end of the secondary epihyal of the fish, the primary epihyal 
being included in the hyomanidubula and the secondary epihyal 
being formed by secondary segmentation from the dorsal end 
of the ceratohyal. 
