874 SKULL 
as proc. zygomaticus, is very variable in size, being largest in the 
Ostrich, Gallinw and Parrots, and smallest in Anseres. In many 
Gallinex both  pro- 
cesses meet at their 
distal end and trans- 
form the temporal 
fossa into a foramen. 
The Periotic 
Bones, enclosing the 
inner EAR (p. 178) 
occupy a space 
bounded — beneath 
by the Basioceipital 
and Basisphenoid, 
in front by the Al- 
sphenoid and Squa- 
mosal (which last to 
a great extent over- 
laps and hides them 
when viewed from 
without), behind and 
above by the lateral 
and supra-occipitals 
and parietals. The 
Periotics consist of 
three distinct  ele- 
ments, which in size, 
relative position and 
in regard to the sur- 
rounding bones ex- 
hibit many modifi- 
Sb, cations, forming a 
very difficult chapter 
of ornithic anatomy 
which as yet has been touched by few,! though an exhaustive study 
of them promises results of prime taxonomic importance. The 
Prootic (Petrosal of some writers) abuts upon the Alisphenoid, and 
with the latter encloses the foramen ovale, through which: passes the 
3rd branch of the nervus trigeminus, while between the posterior margin 
of the Prootic and the anterior border of the Lateral Occipitals les 
the fenestra ovalis,? into which fits the base of the Colwmella of the ear, 
and the fenestra rotunda, Dorsally the Prootic adjoins the Epiotic 
SKULL OF ComMMON FOWL FROM BENEATH. (After Parker.) 
1 Among them are the late Prof. W. K. Parker in several of his numerous 
papers, Prof. Huxley in his Hlements of Comparative Anatomy and Prof. Selenka 
(Bronn’s) Thier-Reich. 
* Inadyvertently called foramen ovale on p. 179. 
