of his figures of this fish, this foramen opening into the internal carotid 
canal while that canal is still enclosed in the cartilage of the lateral wall 
of the pituitary fossa. The trigeminus, facialis and acusticus foramina 
are as shown by GEGENBAUR, but, in my specimen, all three of these 
foramina lie in a single large recess in the lateral wall of the cranial 
cavity, this recess being separated into a small anterior and a large 
posterior portion by a large and low dorso-ventral ridge which lies 
immediately anterior to the foramen faciale, in the lateral wall of 
the recess. ‘The foramen trigeminum is separated into two parts by 
a transverse bar of connective tissue, the dorsal portion transmitting 
the ramus ophthalmicus superficialis trigemini and the ventral one 
the truncus trigeminus together with the nervus profundus. The 
cerebral opening of the acustico-trigemino-facialis recess is not clos- 
ed by membrane, and immediately mesial to the ventral edge of the 
recess the nervus abducens enters a relatively long canal which opens 
in the orbit slightly- ventral to the foramen trigeminum, between it 
and the pituitary foramen, this abducens foramen, not being shown 
by GEGENBAUR. Surrounding these foramina and covering this 
part of the orbital wall there is a tough layer of connective tissue, 
which is perforated by the several nerves above described and also 
by the ramus palatinus facialis and the external carotid artery. 
In my specimen of Mustelus (laevis ?) the pituitary fossa and the 
foramina for the nervi trigeminus, facialis and acusticus are much as 
given by GEGENBAUR in Mustelus vulgaris. The internal carotid 
artery of either side enters the cartilage of the basis cranii by a foramen 
near the middle line and soon joins and fuses with its fellow of the 
opposite side to form a short median trunk. That trunk then separates 
into two parts, each of which runs forward on its own side of the head 
until it is jomed by the dorsal end of the efferent pseudobranchial 
artery, the artery lying, up to and including this point, either in a canal 
in the cartilage or between the cartilage and the linmg membrane of 
the cranial cavity. The efferent pseudobranchial artery perforates 
the cranial wall by an independent foramen, not shown as such by 
GEGENBAUR either in his figures of Mustelus or Galeus, the foramen 
however having quite closely the position of the foramen oculomo- 
torium in the lateral view given by that author of the chondrocranium 
of Galeus. This latter foramen, it will be noticed, lies ventral to 
a line joining the foramina opticum and trigeminum, while the corres- 
pondingly named foramen in the median view given by GEGENBAUR 
