251 
through its posterior opening (foramen lacerum medium), immedi- 
ately enters the sulcus facialis, where it jJoins and accompanies the 
nervus facialis, passing, with that nerve, internal to the hyale, as in 
ganoids and teleosts, and issuing through the foramen stylomastoi- 
deum primitivum. 
The course of the external carotid artery of Echidna is not given 
by Gaupp, but whether it traverses the cavum epiptericum or not, 
it is evident that that chamber of Echidna is in large part the strict 
equivalent of the trigemino-facialis chamber of Amia less the pars 
facialis of the latter, the canalis facialis not, in Echnida, being included 
in the fusions that give rise to the chamber. It is also evident that 
the trigeminus part of the acustico-trigemino-facialis recess of selachi- 
ans forms part of the cavum epiptericum of Echnida, the acustico- 
facialis part of the recess becoming the meatus acusticus internus. 
The ramus palatinus facialis is apparently, in Echidna, wholly ex- 
cluded from the cavum epiptericum, the nerve simply passing across 
the posterior opening of the chamber. The ganglion oticum is said 
to lie partly in the chamber, probably entering it through its posterior 
opening though nothing is said by Gaupp to that effect. Gaupp 
also does not say, so far as I can find, whether or not the anterior 
end of the ganglion is connected with the nervus trigeminus by 
fibers that traverse the cavum epiptericum. If it be so connected, 
it is evident that the connecting nerve strand corresponds, in part 
at least, to the sympathetic nerve that traverses the trigemino- 
facialis chamber in teleosts. 
In man, that posterior extension of the internal jugular vein 
that, in fishes, reptiles and Echidna, issues through the posterior 
opening of the trigemino-facialis chamber or cavum epiptericum, as 
the case may be, is wholly wanting, for the cranial cavity is drained, 
in man, through the foramen jugulare. It would seem however as 
if the posterior opening of the chamber of fishes must in part persist 
in the hiatus Falloppii, which foramen gives entrance into the cranial 
cavity to the large superficial petrosal nerve. That part of the foramen 
lacerum medium that gives exit to that nerve, and that lies between 
the basal portion of the ala temporalis and the auditory capsule, 
would then represent some part of the canal traversed, in ganoids 
and teleosts, by the ramus palatinus facialis. 
Palais de Carnolés, Menton. February 11th 1914. 
