12 
(fig. 4, Hp.P., Pa.P.), there is a marked difference from 
the cod, the former being more prominent than the latter, 
instead of vice versa. 
In a dorsal view (fig. 1) the asymmetry is most pro- 
nounced in front of the parietal region. In the cod the 
frontals completely meet (and indeed fuse) in the mid- 
dorsal line. In the Plaice, on the other hand, there is a 
very wide separation of the frontals anteriorly, so as to 
form a large secondary frontal fontanelle or left orbit. 
The asymmetry is, however, more evident on the 
ventral surface (fig. 2). This is due to the fact that in 
front of the alisphenoids there is no side wall to the 
cranium, which, therefore, here consists ef the paras- 
phenoid only. In front of the prootic the parasphenoid 
turns sharply towards the eyeless side to such an extent 
that the head of the vomer was, in the specimen figured, 
deflected by about a centimetre from the middle line. As 
the parasphenoid is the most prominent feature on the 
base of the cranium, the appearance of torsion in this 
region is, in a full-sized fish, most striking. 
Seen from the side the cranium on the eyeless side 
falls more into one plane than on the ocular, but this is 
obviously due to the inclination of the parasphenoid and 
vomer to that side (cp. fig. 2). 
The interior of the brain case is extremely irregular. 
Owing to the lateral walls meeting ventrally at a some-, 
what acute angle a false floor for the brain becomes neces- 
sary, and this consists of two distinct parts. In front 
there is a rather narrow transverse bridge connecting the 
two alisphenoids, a strong sutural union being effected in 
the middle line. Behind there is a similar but much 
broader bridge joining the two prootics, the two processes 
meeting as before in a median suture. The true floor of 
the cranium is formed in the former of these cases by the 
