Page:An Introduction to the Study of Fishes.djvu/87

Rh irregularly-shaped epibranchial (61). In the fourth arch the hypobranchial is absent. The uppermost of these segments (62), especially of the fourth arch, are dilated, and more or less confluent; they are beset with fine teeth, and generally distinguished as the upper pharyngeal bones. Only the ceratobranchial is represented in the fifth arch or lower pharyngeal. On their outer convex side the branchial segments are grooved for the reception of large blood-vessels and nerves; on the inner side they support horny processes (63), called the gill-rakers, which do not form part of the skeleton.

The scapular or humeral arch is suspended from the skull by the (suprascapula) post-temporal (46), which, in the Perch, is attached by a triple prong to the occipital and mastoid bones. Then follows the (scapula) supraclavicula (47), and the arch is completed below by the union of the large (coracoid) clavicula (48) with its fellow. Two flat bones (51, 52), each with a vacuity, attached to the clavicle have been determined as the (radius and ulna) coracoid and scapula of higher vertebrates, and the two series of small bones (53) intervening between the forearm and the fin as carpals and metacarpals. A two-jointed appendage the (epicoracoid) post-clavicula, is attached to the clavicle: its upper piece (49) is broad and lamelliform, its lower (50) styliform and pointed.

The ventral fins are articulated to a pair of flat triangular bones, the pubic bones (80).

The bones of the skull of the fish have received so many different interpretations that no two accounts agree in their nomenclature, so that their study is a matter of considerable difficulty to the beginner. The following synonymic table will tend to overcome difficulties arising from this cause; it contains the terms used by Cuvier, those introduced by Owen, and finally the nomenclature of Stannius, Huxley, and Parker. Those adopted in the present work are printed in italics. The