The chain of flat bones which, after the removal of the temporal muscles, appear arranged within the inner concavity of the præoperculum (Fig. 24), are comprised with the latter under the common name of _mandibulary suspensorium_. They connect the mandible with the cranium. The uppermost, the _epitympanic_ or _hyomandibular_ (23), is articulated by a double articulary head with the mastoid and posterior frontal. Another articulary head is destined for the opercular joint. The _mesotympanic_ or _symplectic_ (31) appears as a styliform prolongation of the lower part of the hyomandibular; is entirely cartilaginous in the young, but nearly entirely ossified in the adult. The position of this bone is noteworthy, because, directly inwards of its cartilaginous junction with the hyomandibular, there is situated the uppermost piece of the hyoid arch, the stylohyal. The next bone of the series is the _pretympanic_ or _metapterygoid_ (27), a flat bone forming a bridge towards the pterygoid, and not rarely absent in the teleosteous sub-class. Finally, the large triangular _hypo-tympanic_ or _quadrate_ (26) has a large condyle for the mandibulary joint. The palatine arch (Fig. 26) connects the suspensorium with the anterior extremity of the skull, and is formed by three bones: the _entopterygoid_ (25), an oblong and thin bone attached to the inner border of the palatine and pterygoid, and increasing the surface of the bony roof of the mouth towards the median line; it constitutes also the floor of the orbit. The _pterygoid_ (24) (or _os transversum_) starts from the quadrate, and is joined by suture to the _palatine_, which is toothed, and reaches to the vomer and anterior frontal. In the occipital region there are distinguished the _basi-occipital_ (5), readily recognised by the conical excavation corresponding and similar to that of the atlas, with which it is articulated through the intervention of a capsule filled with a gelatinous substance (the remains of the notochord); the _exoccipitals_ (10), articulated, one on each side, to the basi-occipital, and expanding on the upper surface of that bone, so as to meet and support the spinal column; a superficial thin lamella (13), suturally connected with the exoccipitals, not constant in fishes, and erroneously believed by Cuvier to be the _petrosal_ (_os petrosum_) of higher animals; further, the _paroccipitals_ (9), which are wedged in between the exoccipitals and _supraoccipital_. This last bone (8) forms the key of the arch over the occipital foramen, and raises a strong high crest from the whole length of its mesial line; a transverse supraoccipital ridge, coming from each side of the base of this spine runs outwards laterally to the external angles of the bone. The supraoccipital separates the parietals, and forms a suture with the frontals.