OF THE SKULL IK LEPIDOSTEUS OSSEUS. 
489 
hyomandibular and syrnplectic; and tlie upper or styloid end of the cerato-hyal has, 
as in Osseous Fishes, a separate centre, whilst the hypo-hyal has only one , as in 
Lepidosteus ; in Osseous Fishes it has two. 
There are the four normal operculars; the “os mystaceum” is dentigerous and carries 
a jugal in its hinder half. Above the skull, the scutes, which seem to me to be a little 
misunderstood by Professor Bridge, correspond, in essentials, to those of Lepidosteus. 
I should propose the term “ azygous parietal’ 9 for his c/ermo-superoccipital; “squa- 
mosals” for his parietals; and £{ prerostral” for the azygous transverse bone, which, as 
in Lepidosteus, furnishes the snout in front, and which is called by him ethmoid. The 
olfactory capsules are sub-terminal, and the large nasals, which cover them by their 
notched fore margin, are evidently the nasals and “ ethmo-nasals ” of Lepidosteus, in 
one piece, right and left. 
Amia is a true Ganoid, and it has several unmistakable diagnostics even in its skull; 
but it comes very near to the Physostomous Teleosteans. 
Description of the Plates. 
Number 
Plate. 
Eig. 
Stage. 
of times 
magnified. 
30 
1 
1 
Section of the head of an embryo of Lepidosteus 
4 lines long ............ 
30 
V 
2 
1 
A similar section of an embryo 4i| lines long . 
30 
3 
2 
Chondrocranium of an embryo 5 lines long; lower 
view. 
36 
>} 
4 
2 
Section of the head of an embryo lines long . 
30 
)) 
5 
3 
Section of the head of an embryo lines long . 
22L 
)) 
6 
The other half of the same head. 
221 
>) 
7 
3 
Chondrocranium of an embryo f-inch long; lower 
view 
' >»• « • 4 « fl C « -» * « • « • • 
30 
)) 
8 
3 
The same skull; upper view. 
30 
)) 
9 
3 
Head of same embryo ; lower view ..... 
15 
31 
1-15 
3 
A series of vertically transverse sections through 
the head of an embryo 7^ lines long .... 
30 
32 
1 
4 
Chondrocranium of an embryo 1 inch long (nearly). 
24 
Upper view. 
2 
4 
The same object; lower view. 
24 
3 r 2 
