7. _Dermal bones of the skull._--To this category are referred some bones which are ossifications of, and belong to, the cutis. They are the _turbinals_ (20), the _suborbitals_ (19), and the _supratemporals_. They vary much with regard to the degree in which they are developed, and are rarely entirely absent. Nearly always they are wholly or partly transformed into tubes or hollows, in which the muciferous canals with their numerous nerves are lodged. Those in the temporal and scapulary regions are not always developed; on the other hand, the series of those ossicles may be continued on to the trunk, accompanying the lateral line. In many fishes those of the infraorbital ring are much dilated, protecting the entire space between the orbit and the rim of the præoperculum; in others, especially those which have the angle of the præoperculum armed with a powerful spine, the infraorbital ring emits a process towards the spine, which thus serves as a stay or support of this weapon (_Scorpænidæ_, _Cottidæ_). The _pectoral_ arch of the Teleosteous fishes exhibits but a remnant of a primordial cartilage, which is replaced by two ossifications,[10] the _coracoid_ (51) and _scapula_ (52); they offer posteriorly attachment to two series of short rods, of which the proximal are nearly always ossified, whilst the distal frequently remain small cartilaginous nodules hidden in the base of the pectoral rays. The bones, by which this portion is connected with the skull, are membrane-bones, viz. the _clavicle_ (49), with the _postclavicle_ (49 + 50), the _supraclavicle_ (47), and _post-temporal_ (46). The order of their arrangement in the Perch has been described above (p. 59). However, many Teleosteous fish lack pectoral fins, and in them the pectoral arch is frequently more or less reduced or rudimentary, as in many species of _Murænidæ_. In others the membrane-bones are exceedingly strong, contributing to the outer protective armour of the fish, and then the clavicles are generally suturally connected in the median line. The postclavicula and the supraclavicula may be absent. Only exceptionally the shoulder-girdle is not suspended from the skull, but from the anterior portion of the spinous column (_Symbranchidæ_, _Murænidæ_, _Notacanthidæ_). The number of basal elements of each of the two series never exceeds five, but may be less; and the distal series is absent in Siluroids. The _pubic_ bones of the Teleosteous fishes undergo many modifications of form in the various families, but they are essentially of the same simple type as in the Perch. CHAPTER V. MYOLOGY.