364 
its origin, the related part of the palato-quadrate could not well 
represent the dorsal end of the mandibular arch. 
If the processus basalis of amphibians is represented in selachians 
as above set forth, it is evident that the orbital process of selachians 
must be sought for in some other portion of the amphibian palato- 
quadrate. In urodeles it is apparently wholly wanting, unless it be 
represented in some portion of that anterior extension of the pterygoid 
process said by Gaupp (1906, p. 703) to be found in Ranodon, and 
perhaps also in certain of the independent pieces of cartilage said 
by the same author to be found anterior to the pterygoid process in 
certain other urodeles; the pterygoid process of urodeles being simply 
the homologue of some portion of that part of the selachian palato- 
quadrate that lies between the otic and orbital processes. In the 
anurans, GAupP concludes (I. ce. p. 738) that the ethmo-palatine artic- 
ulation of the gnathostome fishes (the related orbital process doubtless 
being included in the part so designated) is the homologue either of 
the commissura quadrato-cranialis anterior of larval anurans, or of 
the “ Verbindung des Proc. pterygoideus mit dem Proc. maxillaris 
posterior,’ the commissura quadrato-cranialis anterior being, in this 
latter case, considered as a provisional larval formation. In mammals 
it would seem as if the orbital process might be represented in some 
part of the vertical plate of the palate bone, for the process and 
its related ligament, in fishes, have closely the same general relations 
to the orbit and to the ethmoid and sphenoid bones that the vertical 
plate has in mammals. 
The ascending process of the amphibian palato-quadrate now 
remains to be considered, and this process is said by Gaupp (1906, 
p. 703) to be characterized by the fact that the so-called first branch 
of the trigeminus runs forward between the process and the side wall 
of the neurocranium, while the second and third branches of that 
nerve run outward behind the process. Because of this relation of 
these nerves to the process, Gaupp (1893, p. 446) concluded that the 
process in amphibians was probably represented in a bridge of carti- 
lage which, he says, in many sharks separates the trigeminus foramen 
into two parts; and he says that this homology was surmised (ver- 
muthet) by WIEDERSHEIM. What WIEDERSHEIM says in the reference 
given (1877, p. 376), is that, in urodeles, the rami I and II of the 
trigeminus pass outward anterior to the process in question, while the 
ramus III alone passes outward posterior to it, which is not in accord 
