CRANIAL NERVES OF SIREN LACERTINA 333 
two amphibians, Amphiuma and Siren. The occurrence in 
these two species of such peculiar structures has some definite 
significance. They suggest a closer relationship between these 
forms than has been suspected hitherto. 
The facial nerve of Siren exhibits a number of peculiar and some- 
what puzzling characteristics. Siren is the only urodele in which 
is found a levator muscle of the hyoid arch. This is innervated 
by a branch of the ramus jugularis VII. As Driiner suggests, 
this may have no especial significance, but be merely one of the 
peculiarities in structure of this form. 
The lateral line anastomosis of the seventh nerve with the 
tenth nerve (VII ad X) may be interpreted as the persistence 
of aramus oticus of fish-like ancestors, or it may be looked upon as 
incidental. 
The contribution of maxillaris and buccalis fibers to the pro- 
fundus-palatine anastomosis has such a closely corresponding 
arrangement in Triton (Coghill) and also in Salamandra, if von 
Plessen and Rabinovicz’s figures be correct, that it can hardly 
be explained as incidental. Excluding the maxillaris and buccalis 
fibers, the profundus-palatine anastomosis is of such a character 
as to make it certain that Coghill discovered in Amblystoma its 
typical urodelan relations. 
The ramus alveolaris VII in Siren is not, as has been assumed 
by some, essentially different from the corresponding nerve in 
the Urodela in general, but, as in Necturus, owing to the imper- 
fect development of the opercular (splenial) ossicle, the alveolar 
branch proper is not confined to a canal in the jaw and in conse- 
quence does not form a definite anastomosis with an alveolar 
branch of the ramus mandibularis V. Yet both the trigeminal 
and the facial alveolar branches are present and in such a position 
that if the operculare were in its fully developed urodele condition, 
they would be enclosed by it. Bender (’06) undoubtedly inter- 
prets correctly the origin of the anastomosis between these two 
branches as due to the development of membrane bones around 
Meckel’s cartilage and the confining of the nerves in a canal, for 
the primitive arrangement is doubtless that found in the lower 
selachians where the two nerves are free and without anastomoses. 
