NECTURUS MACULATUS. ALT 
process is in the form of a flattened splint and is superposed upon the dorsal surface 
of the anterior end of the frontal, lying in a shallow groove formed for its reception. 
This is the only contact between the premaxillary and any of the other bones of the 
skull; but the extreme tips of the rostral cartilages may touch its ventral surface, and 
the two premaxillaries almost touch each other at their antero-internal angles. 
2. THE PALATO-PTERYGOID ARCH. This arch in Urodeles consists typically of three 
dermal elements, vomer, palatine, and pterygoid, but owing to fusion or loss of one or 
more of the elements, it usually appears in a modified form. In some Urodeles the first 
two of the typical elements fuse and form a broad vomero-palatine, while in others, as is 
the case in Necturus, the vomer is distinct and the second and third elements fuse to form 
a palato-pterygoid. Usually in the vicinity of the pterygoid there is a part of the primitive 
cartilaginous palato-pterygoid arch around which the dermal bones may be supposed to 
have originated, and this is denominated the “ cartilaginous pterygoid.” In a few cases 
(Desmognathus, Batrachoseps) the osseous pterygoid fails, leaving the vomero-palatine 
as the sole dermal representative of the arch. 
a. Vomer.—The main portion of this bone is somewhat triangular in shape and 
forms the extensive, flattened palatine portion. Added to this upon its outer border 
appears the alveolar portion, set at right angles to the main part and slightly curved. 
The palatine portion forms the greater part of the anterior third of the roof of the mouth 
but the two bones do not meet in the mid- 
dle line. The inner borders, forming the 
longest side of the triangle, are quite near 
one another anteriorly but diverge posteri- 
orly, and in the space thus left appears the 
parabasale, which also extends along the | ny cya 
dorsal side of the palatine process of the yy °F PB. 
vomer, thus doubling the bony roof of the 
palate over a large extent of the anterior 
surface. The parabasal does not, how- 
ever, extend anteriorly as far as the vom- 
erine teeth, and there is thus left a consid- 
erable interval, bounded by the above 
mentioned teeth, the inner borders of the 
vomers, and the anterior border of the DORSAL. 
¢ ; ; VENTRAL. 
parabasal, where there is no bony roof. ; a i 
: Fig. 17. Two views of right vomer. 3. Contact sur- 
This opening is nearly square, and through faces with other bones are designated by an x. 
it, in the prepared skull, there may be 
