DR. TRAQUAIR ON THE ASYMMETRY OF THE PLEURONECTIDÆ. 293 
Fig. 14. Frontal bones of the Plaice, the position of the eyes in relation to them being indicated in 
dotted outline. Lettering as in fig. 7. 
Fig. 15. Frontal bones of the Pole (Platessa pola), showing a condition, of the interocular process of the 
bone of the eyeless side, intermediate between that in the Halibut (fig. 11) and in the Plaice 
(fig. 14). 
Fig. 16. Cranium of the Cod (Gadus morrhua), seen from the left side. 
Nasal part of the cranium : c, olfactory foramen. 
Orbital portion, the interorbital fibrous septum being indicated in dotted shading. 
The brain-cavity and auditory part of the cranium. 
Fig. 17. Left prefrontal of the Cod, disarticulated. 
a. Process going upwards and backwards to join the frontal. 
b. Process going downwards and backwards to join the basi-presphenoid. 
c. Process to join the ala of the vomer. 
dd. Two processes going towards the nasal bone, with an olfactory notch (c) between them. 
e. Process to which is attached the anterior suborbital bone. 
The representatives ofthese processes in the prefrontal bones of the flatfish are marked with the same 
letters in the preceding figures. Note, that in the Cod there is no representative of the process f 
in the flatfish. 
PLATE XXX. 
Fig. 1. Suspensory, palatine, and opercular bones of the ocular side in the Turbot. Cartilage shaded with 
horizontal lines. 
Fig. 2. The same bones, but of the eyeless side. 
Fig. 3. Front view of the cranium and palato-suspensory apparatus of the Halibut, to show the greater 
flatness of the latter bones on the eyeless side, the greater elevation on the same side of the 
olfactory foramen (c), the articulation of the palate-bone to the prefrontal, and of the articu- 
lation of the lower jaw to the trochlea (*) on the hypotympanic. 
Fig. 4. Suspensory, palatine, opercular apparatus, and jaws of the eyed side of the Plaice, drawn from 
dried specimens. 
Fig. 5. The corresponding bones on the eyeless side. 
Fig. 6. Lower jaw and opercular apparatus of Plaice, seen from below. 
Fig. 7. Cranium and palato-suspensory apparatus of Plaice, seen directly from the front. Lettering as 
in fig. 3. 
PLATE XXXI. 
Fig. 1. Opercular and oral apparatus of the Halibut, together with the “ superficial face-bones,” as seen 
on the ocular side. 
aa. Tubular scales of the lateral line. 
72. Supratemporal chain. 
73'. Suborbital chain of the right or lower eye. E 
13a. Anterior right suborbital, very much larger than the rest, from which it is separated by an — 
It has no connexion with the mucus-canal. 
19, Right * turbinal ” ossicle, or os terminale. 
19. Left turbinal, situated on the top of the snout. 
^. Retractor maxilla muscle. 
B. Masseter, 
e. Right olfactory foramen. j 
e. Point at which the supratemporal mucus-canal sends down a branch to join the cross commissure, 
