184 
ME. W. E. HARKER ON THE STRUCTURE AND 
Plate. 
Pig. 
Stage. 
Humber of times 
magnified. 
17 
12 
6 
Pt ery go - quadrate plate of old individual 
of Acipenser sturio; outer view . 
J natural size. 
55 
13 
6 
The same; inner view. 
natural size. 
18 
1 
6 
Bight orbital region of old specimen . 
\ natural size. 
5 5 
2 
6 
Left orbital region of old specimen 
natural size. 
33 
3 
5 
Basis cranii, orbital region, in adult Aci- 
penser sturio . 
Slightly enlarged. 
55 
4 
5 
Palato-quadrate apparatus of same, from 
above . 
Slightly enlarged. 
55 
5 
5 
Visceral arches of same, side view. 
§ natural size. 
55 
6 
5 
The same; section of hyomandibular . 
Slightly enlarged. 
3? 
7 
5 
The same; section in another specimen . 
Slightly enlarged. 
55 
8 
5 
Mandible of same; inner view .... 
Slightly enlarged. 
55 
9 
5 
Section of cerato-hyal of same .... 
Slightly enlarged. 
55 
10 
5 
Visceral arches of same, from below . 
Slightly enlarged. 
