Three species are known: _Ch. monstrosa_, from the coasts of Europe and Japan and the Cape of Good Hope; _Ch. colliei_ from the west coast of North America; and _Ch. affinis_ from the coast of Portugal. (See Fig. 96, p. 184.) CALLORHYNCHUS.--Snout with a cartilaginous prominence, terminating in a cutaneous flap. Two dorsal fins, the anterior with a very strong and long spine. Extremity of the tail distinctly turned upwards, with a fin along its lower edge, but without one above. Anal fin close to the caudal, short and deep. One species (_C. antarcticus_) is common in the Southern temperate zone. Cunningham describes the egg (see Fig. 81, p. 169), as being of a dark greenish-black colour, and, in general, measuring from eight to nine or even ten inches in length, by about three in breadth. It consists of a central, somewhat spindle-shaped convex area (between the horny walls of which the young fish lies), surrounded by a broad plicated margin, which is fringed at the edge, and covered on the under surface with fine light brownish-yellow hairs. SECOND ORDER--GANOIDEI. _Skeleton cartilaginous or ossified. Body with medial and paired fins, the hinder pair abdominal. Gills free, rarely partially attached to the walls of the gill-cavity. One external gill-opening only on each side; a gill-cover. Air-bladder with a pneumatic duct. Ova small, impregnated after exclusion. Embryo sometimes with external gills._ To this order belong the majority of the fossil fish remains of palæozoic and mesozoic age, whilst it is very scantily represented in the recent fauna, and evidently verging towards total extinction. The knowledge of the fossil forms, based on mere fragments of the hard parts of the body only, is very incomplete, and therefore their classification is in a most unsatisfactory state. In the following pages only the most important groups will be mentioned. [For a study of details we have to refer to _Agassiz_, “Poissons Fossiles;” _Owen_, “Palæontology,” Edinb. 1861, 8vo; _Huxley_, “Preliminary Essay upon the Systematic Arrangement of the Fishes of the Devonian Epoch,” in Mem. Geolog. Survey, Dec. 10; Lond. 1861, and “Illustrations of the Structure of Crossopterygian Ganoids,” _ibid._ December 12, 1866; _Traquair_, “The Ganoids of the British Carboniferous Formations,” part I. “Palæoniscidæ.” Palæontogr. Soc. Lond. 1877.] Eight suborders may be distinguished at present. FIRST SUB-ORDER--PLACODERMI. _Extinct. The head and pectoral region of the body encased in great bony, sculptured plates, with dots of enamel; the remainder of the body naked, or with ganoid scales; skeleton notochordal._