30 
head of the maxilla is brought into closer connection with 
the posterior ascending process of the pre-maxilla. Then 
again the posterior articular process for the maxilla at the 
junction of the two arms of the pre-maxilla is smaller, and 
instead of overlapping the maxilla is overlapped by it. 
Pre-Maxilla.—Both arms are longer and stouter. The 
ascending arm is at right-angles to the oral arm instead 
of at an obtuse angle as on the right side, and passes over 
the inter-maxillary more to the middle line of that car- 
tilage. It bore in this specimen 17 teeth as against 4 of 
the other side, and set, as already stated, in a different 
plane. 
The asymmetry of the suspensory and jaw apparatus, 
whilst undoubtedly initiated by the torsion cf the 
cranium, has also been independently emphasized by the 
habits of the fish, as already described. The broad 
anatomy of this distortion is as follows: (1) The suspen- 
sory apparatus on the right side is mostly longer—thus 
thrusting the jaws over to the left; + (2) the motion of the 
maxille at the sides of the mesethmoid prominence and 
over the head of the vomer and the course of the inter- 
maxillary over the mesethmoid beak itself is an oblique 
one with a set towards the left, which the pre-maxillz and 
mouth must necessarily follow. The jaws themselves and 
the bones immediately related to them are naturally more 
robust on the left side, since their function is mostly per- 
formed on that side. Hence the practical absence of teeth 
on the right pre-maxilla and dentary. | 
4.—THE OpEercuLAR Bones (Fig. 5). 
Ocular Side. 
Operculum (Op.).—A thin laminate bone containing 
no cartilage except at the articular cup. It is bifid pos- 
+ Cp. Traquair, op. cit., Tab. 30 and pp. 276-7, 
