370 
In Amia the parasphenoidal leg of the alisphenoid rests in part 
on a process of the lateral wing of the parasphenoid (Auuıs, 1897a, 
p. 493); and the relation of this wing of the parasphenoid to the 
bounding wall of the trigemino-facialis chamber, in ganoids and teleosts, 
would seem to support Gaupp’s (1902) contention that the mammalian 
pterygoid is derived, in part at least, from that bone of lower verte- 
brates. 
Fucus concludes that the ramus maxillaris trigemini of mammals, 
to acquire its position anterior to the ala temporalis, has slipped 
forward over the dorsal end of the antipterygoid (ala temporalis). 
JAEKEL (1913) has recently stated his conclusion that there are 
four preoccipital, or facial, segments represented in the vertebrate 
skull, and that they are each related to paired sensory organs: the first 
to a prenasal organ (JAcoBsoN’s organ), the second to the nose, the 
third or mandibular segment to the eye, and the fourth or hyoid seg- 
ment to the ear and the latero-sensory canals (Stammäste der Tremal - 
kanäle). I had already prepared a somewhat similar suggestion be- 
fore seeing JAEKEL’s article, but the four sensory regions of the head, 
as I find them, are the nasal, optic, facialis latero-sensory and auditory. 
Bach of these regions, in Amia, is bounded both anteriorly and poste- 
riorly by a more or less complete cartilaginous partition placed approxi- 
mately perpendicularly to the axis of the body. The nasal compart- 
ment has related to it the palatine process of the palato-quadrate; 
the optic compartment has related to it the orbital process; the latero- 
sensory compartment the processus basalis; and the auditory com- 
partment the hyoid arch. The ala temporalis would then form the 
outer wall of the latero-sensory compartment, and the related pro- 
cessus basalis would be the dorsal end of the mandibular arch. And 
anterior to this mandibular arch, there would be, if the sensory 
compartments are of segmental value, two more arches represented 
in the selachian palatoquadrate; and it is of interest to note that 
the rami maxillaris and ophthalmicus profundus trigemini would 
seem to be related respectively, in their distribution, to the second 
and first of these two arches. This arrangement of these preoccipital 
segments would differ from that shown in the schematic represen- 
tation given by JAEKEL in that the basal process and not the otic 
process would represent the dorsal end of the mandibular arch, and 
that the second and first arches would be related to the eye and 
nose, respectively, instead of to the nose and a prenasal organ. 
