Elementary text-book of zoology. Special part: Mollusca to man / by C. Claus ; translated and edited by Adam Sedgwick ; with the assistance of F.G. Heathcote.
- Carl Friedrich Wilhelm Claus
- Date:
- 1897
Licence: Public Domain Mark
Credit: Elementary text-book of zoology. Special part: Mollusca to man / by C. Claus ; translated and edited by Adam Sedgwick ; with the assistance of F.G. Heathcote. Source: Wellcome Collection.
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![fibres of the other without forming a chiasma. The gills are usually comb-shaped, and, as in the Ganoids, lie freely in a branchial cavity under a branchial operculum, to which is added a a branchiostegal membrane, supported by branchiostegal rays. The skeleton is char- acterised by the well separated, usually bony vertebrae, and by the bony skull, beneath which remains of the primitive cartilaginous cranium often persist. The skin is only rarely naked or apparently without scales. In such cases the scales are very small and do not project from the surface; more frequently bony plates and scutes are present in it, especially behind the head. As a rule the skin is covered by cycloid or ctenoid scales which overlap one another. The urinary and genital organs open behind the anus either separately or by a common aperture on a urogenital papilla. [The kidney is dilated in front to form a head-kidney, which, however, is in the adult, sometimes if not always, largely composed of a tissue resembling lymphatic tissue (Balfour). The generative ducts are continuous with the investments of the generative glands in both sexes, and in the male there is no connection between the testis and the kidney.] Only a few Teleosteans are viviparous; they almost all lay small eggs in enormous numbers in protected places. Sub-order 1. Lophobranchii. Teleo- steans with armoured skin, elongated tubular snout which is without teeth. The gills are in the form of tufts and the gill slits are very narrow. with the brood-pouch (Brt). Fam. Pegasidae. The body is flattened ; pectoral fins large, spread out like wings ; pelvic fins small. Pegasus volans L., East Indies. Fam. Syngnathidae, The body is cylindrical or laterally compressed. The gill openings narrow, and pectoral fins small ; males with brood-pouches (fig. 609). Syngnatlius acus L., Pipe-fish ; Hippocampus antiquorum Leach., Sea-horse, Mediterranean. Sub-order 2. Plectognathi. Globular or laterally compressed Teleosteans, with immovably fused maxilla and prsemaxilla, and narrow mouth. The dermal armour is strong and often bears spines. There are usually no pelvic fins. The gills are comb-shaped,](https://iiif.wellcomecollection.org/image/b2813378x_0169.jp2/full/800%2C/0/default.jpg)
