590 EDWARD PHELPS ALLIS, JR. 
represent the dorsal, epi-pharyngeal portion only of the carti- 
laginous bar of that arch. Van Wijhe (’01) says that it repre- 
sents the dorsal half of the hyal, or first postmandibular arch, 
that the ventral half of that arch entirely aborts, and that the 
epihyal and ceratohyal of Gegenbaur’s and Parker’s descrip- 
tions of the adult represent the cartilaginous bar of a hyobran- 
. chial arch which lies between the hyal and first branchial arches. 
In the adult of Raia clavata, Parker (’76) shows the hyoman- 
dibula in a position practically parallel with, but considerably 
ventro-lateral to, the pharyngobranchials. It articulates dor- 
sally with the neurocranium, and in Raia radiata-I find this ar- 
ticulation ventral to the vena jugularis and dorsal (lateral) to 
the lateral dorsal aorta. The ventro-anterior end of the hyo- 
mandibula is attached by ligament to the articulating ends of 
the mandibula and palatoquadrate, and this attachment is said 
by Parker (1. ¢., p. 220) to be primarily with the quadrate. 
The dorso-posterior end of the hyomandibula is shown much 
larger than the ventro-anterior one, and in addition to articulat- 
ing with the neurocranium it is attached by a single ligament, 
both to the dorsal end of the epihyal and to the adjacent dorsal 
end of the epibranchial of the first branchial arch. Parker calls 
this the interhyal ligament, thus homologizing it with the liga- 
ment which, in ganoids and teleosts, connects the dorsal end of 
the ceratohyal, through the intervention of a cartilaginous inter- 
hyal (stylohyal), either with the symplectic or with the hyoman- 
dibula of those fishes, but he says that no cartilage is developed 
in the ligament in the Batoidei. There are no branchial rays re- 
lated to the hyomandibula either in Raia or any others of the 
Batoidei, but there is a dorsal extrabranchial related to this 
arch. 
In the adult of Torpedo marmorata (Gegenbaur ’72) the con- 
ditions that it is important to here consider differ from those in 
Raia only in that there is a hook-like process on the anterior edge 
of the hyomandibula, and, as this process is also shown by Dohrn 
(85, pl. 1, fig. 2a) in his figures of embryos of Pristiurus in 
which the tissues are still in a procartilaginous condition, it is 
evidently an early acquisition in these fishes. In Narcine it is 
