No. 3.] 
The paroccipital, Owen, of fishes 
is called by Professor Huxley ‘ epi- 
otic,” and considered the homologue 
of the ‘‘ epiotic” in Labyrinthodon- 
tia; the homologue of that portion 
of the supraoccipital which lodges a 
part of the upper semicircular canals 
in the Monocondylia; the homologue 
of one part of the squamosal in 
Mammals. 
The petrosal of Owen and former 
authors is called ‘‘ prodtic” by Pro- 
fessor Huxley. 
The “intercalare” (Vrolik) in fishes 
is called by Professor Huxley opzstho- 
tzc, and considered as the homologue 
of the paroccipital in the Monocon- 
dylia. 
Aug. 30, 1889. 
VERTEBRATE-SKULL. 
471 
The Jaroccipital, Owen, of fishes, 
is the paroccipital in Batrachia and 
Monocondylia and the ‘‘ mastoid” 
portion of the squamosal in Mam- 
mals. The paroccipital of the Ba- 
trachia is free in the Proteida, but 
co-ossified with the exoccipital in the 
other living representatives. In the 
Stegocephalia it may be free, or unit- 
ed with the exoccipitals. The so- 
called ‘‘ epiotic”” in the Stegocephalia 
is only a dermal plate covering the 
paroccipital, which ought to be named 
the paroccipital plate.! 
The supraoccipital of the Mono- 
condylia consists of this element alone, 
and not of more. 
I retain the name Zetrosal. 
The “intercalare” (Vrolik) in fishes 
is the homologue of the stapes in all 
higher vertebrates, and the name in- 
tercalare ought to be used in prefer- 
ence to columella or stapes for all 
vertebrates. 
2. THE TEMPORAL ARCHES. 
In the oldest Batrachia, the Stegocephalia, we find a continu- 
ous dermal covering of the upper and lateral parts of the skull. 
This covering is interrupted by five openings, —the two nasal 
openings, the orbits, and the single parietal foramen: the same 
conditions we have to expect in the ichthyic ancestors of the 
Batrachia ; forms like Lepzdosteus would express such a stage. 
The dermal bones of such a skull have been developed from 
scales, and must have been very numerous at first ; later blend- 
ing of elements, or enlargement of some at the cost of others, 
took place, and the number was reduced. In the Stegocephalia 
the number of these dermal ossifications is nearly constant. 
The bones which interest us in the question about the temporal 
arches are the following: parietals, frontals, post-frontals, post- 
1 Among the Monocondylia the paroccipital is free in the Ichthyosauria and 
Testudinata, but united with the exoccipital in the rest. 
