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undissected fish. The right frontal, like the left, is 
bounded by the frontal of the other side, supraoccipital, 
parietal, sphenotic, alisphenoid, the prefrontal of its side 
and median ethmoid, except that the left frontal does not 
reach the median ethmoid. 
Left Frontal (L.F'r., figs. 1, 2, 3).—Takes no part in 
forming the interorbital ridge. Compared with the right 
frontal it is broad from side to side and shorter from 
before backwards. As shown in figs. 1 and 2, it sends out 
on the right a strong transverse process which overlaps 
the dorsal surface of the right frontal. The forward 
process on the left of the left frontal lying over the left 
prefrontal, together with the posterior portion of the latter 
bone, are lying apparently in a very anomalous position, 
i.e., they are situated under the left eye instead of over it. 
This, however, has been produced by the frontal growing 
forwards, and the prefrontal growing backwards, after the 
torsion of the cranium was an accomplished fact. It is 
thus a precisely analogous case to the anomalous position 
of the anterior extremity of the dorsal fin. 
Prefrontal (/?. and L. P.F'r., figs. 1, 2, 3)—The left 
prefrontal is in every respect larger than the right—due 
apparently to the circumstance just mentioned. Both 
contain in front some cartilage which is continuous with 
what we have termed the ethmoid cartilage. Both also 
are perforated by a foramen transmitting the olfactory 
nerve to the olfactory lamin of the nasal organ, the left 
foramen being perceptibly smaller than the right—due 
to the lett olfactory nerve being so much smaller than the 
right. The left prefrontal fits by means of a long narrow 
backward process into a groove on the dorsal surface of the 
front end-of the parasphenoid—a process entirely absent 
on the right side. The articular surface for the lachrymal 
is smaller on the left side, and similarly the process 
