302 EDWARD PHELPS ALLIS, JR. 
development of this bar of cartilage doubtless accounting for 
the suppression of a posthypophysial commissure between the 
pituitary veins of opposite sides of the head. | 
The so-called parasphenoid of Echidna is considered by Gaupp 
(05 a) to be the homologue of the ascending process of the 
parasphenoid of the Sauria, and also of the mammalian ptery- 
goid, the latter bone not being the homologue of the pterygoid 
of reptiles. The bone of Echidna is said to lie, in embryos, 
directly upon the cartilage of the basis cranii, without inter- 
vening connective tissue, and later to fuse with the sphenoid 
(Keilbein) as part of its processus pterygoideus. No cartilage 
has been found in this bone in Echidna, but it is said to be found 
in the pterygoid of mammals. The bone lies anterior to the 
foramen caroticum, the internal carotid arteries accordingly 
not coming into any relations to it. The nervus parabasalis 
(palatinus facialis) is said to run forward external to the pos- 
terior portion of the bone, but, anterior to the point of exit of 
the nervus opticus from the cranial cavity, it perforates the 
bone through a foramen parabasale, and so enters the anterior 
portion of the cavum epiptericum. There is thus no canalis 
parabasalis in this animal, and the relations of the parasphenoid 
to the chondrocranium, to the internal carotid arteries, and to 
the ramus palatinus facialis all show that it corresponds to the 
ascending process of the parasphenoid of Amiurus, and to the 
mesial plate of that process of the parasphenoid of Polyp- 
terus, and that it is accordingly an ossification in the roof of a 
ventral myodomie cavity and not in its floor. 
CARTILAGINES POLARIS AND ACROCHORDALIS 
Polar cartilages were, as already stated when describing the 
Selachii, first described by van Wijhe (’05) in embryos of Acan- 
thias, where the cartilage of either side is said by him to lie be- 
tween the trabecular and parachordal cartilages, but it soon 
fuses with both those cartilages and then forms, with the tra- 
becula, the ventral border of the orbital fenestra. The pos- 
terior border of the orbital fenestra is said to be formed by the 
lamina antotica, which is an outgrowth of the anterior end of 
