The number of haemal arches present in the caudal lobe varies much, e. g. the Cod and Stickleback have only two. The 'accessory' rays are in some instances of large size, e.g. in the Cod, and the caudal fin has then a peculiar rounded appearance.
The series of bones known as supra-clavicle, clavicle, inter-clavicle, and post-clavicle in Teleostei and Ganoidei appear one and all to be derived from the integument and mucous membrane of the branchial cavity. In the Teleostei they are dermal in position; in Acipenser on the contrary their outer surface resembles in appearance the bony plates of the integument, and the bone has also the same structure. Recent researches appear to have established the fact that the clavicle of higher forms is a process of the cartilaginous shoulder-girdle (see Gotte and Hoffmann's papers referred to under Pigeon, p. 67). Such a process exists in the Sturgeon, and is named prae-coracoid in Professor W. K. Parker's Monograph on the shoulder-girdle. 'Swirski's researches on the shoulder-girdle in the Pike appear to establish the fact that the true coracoid aborts almost completely in that Teleostean, and therefore probably in others as well, while the clavicular process (= praecoracoid process of his paper) increases in size, and forms what is generally termed coracoid. The dorsal angle of the scapula of the Pike bends inwards and downwards in development. In Cyprinoids, in the Salmon, etc, a curved bar of bone stretches from the dorsal angle of the scapula to a spot ventral to the scapular foramen.
This bar in the Cyprinoid is derived, according to 'Swirski, from two processes of the scapula, a dorsal and a ventral, which meet and fuse. They appear in a late stage of development.
In the bony Ganoidei the proximal end of the metapterygium of the ventral fin bears a cartilaginous process. Davidoff regards this as pelvic, but Wiedersheim considers it to be part of the metapterygium. The two metapterygia are always in contact at their proximal extremities, but often widely separate distally, e.g. bony Ganoidei, the Pike, etc.; or a bar of bone may develop at the distal end of each metapterygium, and meet its fellow in the middle line, while a space separates the middle portion of the two bones, e. g. Salmon j or the two may be in contact throughout the whole extent of their median edges, e. g. in the Perch; or finally, complete fusion may take place.
The basal cartilages or bones which articulate with the coraco-scapular are five in number. The first is included in the first fin-ray, and represents a propterygium; the fifth is long and is a metapterygium. In some Teleostei the number is reduced, or the bones may be entirely lost. A row of small radial cartilages is to be found in some instances inclosed in the bases of the fin-rays. They do not seem to be present in the Perch, at least not in the adult. The fin-rays of the pelvic fins articulate directly with the metapterygium. A row of excessively small bony or cartilaginous particles representing radials is sometimes inclosed in their bases. They do not exist however in the full-grown Perch.
For the caudal canal and interspinous bones, see next Preparation, pp. 100, 101.
Skull of Salmon.W. K. Parker, Ph. Tr. 163, 1873; cf. Id. and Bettany, Morphology of the Skull, London, 1877. Cod. T. J.Parker, Zootomy, London, 1884. Pike (and other fish). Huxley, Lectures on Elements of Comparative Anatomy, 1864. Investing bones of Pike's head. Walther, J. Z. xvi. 1882. Loricaria, etc. Goldi, ibid. xvii. 1883. Characinidae (and auditory bones). Sagemehl, M. J. x. 1885.
Azygos fins.Kolliker, Uber das Ende der Wirbelsaule der Ganoiden, etc, Leipzig, 1860. Caudal. Lotz, Z. W. Z. xiv. 1864 (Perch, p. 89); Development of; Agassiz, Proceedings Amer. Acad. (new series) v. 1878; vi. 1879: ix. 1882; cf. Balfour and W. N. Parker on Lepidosteus, Ph. Tr. 173, 1882, and Grassi, M. J. viii. 1882.
Fatty fin of Salmonidae.De la Valette St. George, A. M. A. xvii. 1880.
Ichthyopterygium and Cheiropterygium. Baur. Z. A. viii. 1885; cf. Balfour in Comparative Embryology, ii. pp. 500-511 with references.
Shoulder-girdle.'Swirski, Schultergurtel des Hechtes (Inaug. diss.), Dorpat, 1880; W. K. Parker, Ray Society, 1868; Gegenbaur, Untersuchungen zur Ver-gleich. Anat. der Wirbelthiere, ii., Leipzig, 1865.
Pelvis.Wiedersheim, M. J. vii. 1881; von Davidoff, M. J. v. 1879; vi. 1880.