564 EDWARD PHELPS ALLIS, JR. 
extravisceral, thus employed, has been properly objected to, but 
as the term visceral is currently applied, not only to all of these 
arches themselves, but also to their inner cartilaginous bars, 
there would seem to be no good reason for not applying it also 
to the external cartilaginous bars.. But as, with equal reason, 
the branchial and branchiostegal rays would then have to be 
collectively called the visceral and viscerostegal rays, I retain 
the term extrabranchial for these cartilages in whatever arch 
they may be found. Branchial, hyal and visceral I employ as 
proposed by Gaupp (’05). 
The vena jugularis, which seems to have had a markedly im- 
portant. influence on the development of the definitive carti- 
laginous bars of the prebranchial visceral arches, is not always, 
in the different orders of fishes, formed by the fusion of identical 
sections of the venae cardinalis anterior and capitis lateralis of 
embryos, the former vein being the primitive one and being 
said to lie ventro-mesial to the roots of all of the cranial nerves, 
while the latter one is of secondary formation and is said to lie 
dorso-lateral to those roots (Hochstetter ’06). The definitive 
vein also has, in certain fishes, different relations to the hyoman- 
dibula, as I have quite recently had especially called to my at- 
tention, lying dorso-external to the hyomandibula in Chlamy- 
doselachus but ventro-internal to that element in Amia and tele- 
osts (Allis 714 b, p. 235). Wishing to know if these differences 
in the relations of the vein to the cranial nerves and to the - 
hyomandibula were in any way related to each other, I have had 
the relations of the vein to the trigeminus and posttrigeminus 
nerves traced in a certain number of fishes. 
In the Selachii and Batoidei the definitive vena jugularis is 
said by Hochstetter (’06) to be formed entirely by the vena capi- 
tis lateralis and to agree in this with the definitive vein in Tro- 
pidonotus and the Mammalia. In Mustelus (probably laevis) I 
find the vein lying dorsal to all of the components of the nerves 
here under consideration, excepting only the latero-sensory fi- 
bers which, in their exit from the cranium and in their peripheral 
distribution, are associated with the nervi trigeminus, glossopha- 
ryngeus and vagus. The vein lies ventral to all of these latero- 
