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 ICHTHYOLOGY 161 C. L. Bonaparte (Rome, 1831) comprised the or- ders: L, acanthopterygii, with 17 families; II., malacopterygii, with 12 families; III., plecto- gnathi, with 2 families ; and IV., cartilaginei, with 5 families; including in all nearly 3,600 species. The principal improvement on the system of Cuvier is in the series in which the genera are placed. Swainson (" Monocardian Animals," in Lardner's " Cyclopaedia," 1838-'9), true to his quinary system, divides fishes into the five orders acantkopteryges, malacopteryges, cartilagines, plectognathes, and apod.es. Straus- Durckheim (Traite (K anatomic comparative, Paris, 1843) adopts the eight orders of Cuvier, but subdivides the chondropterygians with fixed branchiae into three orders, and separates the sharks as the order seloxiens, the rays as the order batoides, and the cyclostomes as the order galexien* (from Gr. ya/U<if, lamprey), the term cycloatoma having been used for a gasteropod mollusk; he thus makes ten orders. Rymer Jones (in the article "Pisces" in the "Cyclo- pjedia of Anatomy and Physiology," 1847) adopts a modification of Cuvier's system. He makes three divisions: I., chondropterygii or cartilaginous fishes ; II., osteopterygii or bony fishes; III., dermapterygii, with skeleton car- tilaginous or membranous, and with orders cyclostomata (lampreys) and Iranchiostomata. About 1830 Prof. Agassiz, principally from the study of fossil fishes, established a classifi- cation based on the characters of the scales, as follows: order 1, placoids, corresponding to the cartilaginous fishes of authors, but ex- cluding the sturgeons; 2, ganoids, including the sturgeons, and especially the fossil genera with enamelled scales; 3, ctenoids, comprising bony fishes with scales pectinated on the pos- terior border, and corresponding generally to the acanthopterygians of Artedi, exclusive of the scomberoids, labroids, and pleuronectes ; 4, cycloids, including the malacopterygians with the above exceptions, and exclusive of the blennioids and lophioids. This system, soon abandoned as an exclusive one by its author from its placing too much stress on external characters, was valuable as connecting in a continuous series living and fossil fishes, and led to the discovery of many important rela- tions between the scales and the internal or- gans. The system of Johannes Muller, as given in -the Berlin "Transactions" for 1844, derives its characters from anatomical struc- ture, leading often to combinations without re- gard to zoological differences. He makes six subclasses: I., dipnoi; II., teleostei ; III., ga- noidei ; IV., elasmo-branehii or selachii; V., marsipobranchii or cyclostomi; VI., lepto- cardii. Siebold and Stannius adopt this clas- sification in their "Comparative Anatomy;" and a slight modification of it may be found in the third volume of the " Organic Nature " in Orr's "Circle of Sciences," 1855. Owen's classification, mentioned below, and adopted by Sir John Richardson in the article "Ich- thyology" of the " Encyclopaedia Britannica," is based partly on that of Muller. Vogt, in his Zoologische Briefe (1851), divides fishes into the orders leptocardia, cyclostomata, selachia, ganoidea, and teleostia. Van Beneden's em- bryological system (1855) is nearly the same ; his orders are plagiostomi, ganoidei, teleostei, cyclostomi, and leptocardii. Van der Hoeven's classification (as given in the English transla- tion of his "Handbook of Zoology," 1858) makes fishes the 14th class of the animal king- dom, and divides them into 5 sections, with 11 orders and 46 families. The sections are der- mopterygii, chondropterygii, ganolepidoti, os- teopterygii, and protopteri. Milne-Edwards, in his Cours elementaire d'hiitoire naturelle (1855), divides fishes into osseous and cartila- ginous; the former includes the orders acan- thopterygii, abdominales, subbrachii, apodes, lophobranchii, and plectognathi ; and the lat- ter, the orders sturiones, selachii, and cycloito- mi. Owen's classification in his " Lectures on Comparative Anatomy" (1855) made the or- ders dermopteri, malacopteri, pharyngognathi, anacanthini, acanthopteri, plectognathi, lopho- branchii, ganoidei, protopteri, holocephali, and plagiostomi (sharks and rays). His classifica- tion of 1866 is somewhat different, as follows : In the division hcematocrya, or cold-blooded animals, including fishes, batrachians, and rep- tiles, in the fishes he makes subclasses: 1, der- mopteri, with orders cirrostomi (lancelet) and cyclostomi (lampreys) ; 2, teleostomi, with or- ders malacopteri (soft-rayed fishes), anacan- thini (cod), acanthopteri (spiny-rayed fishes), plectognathi (ostraceans), lophobranchii (pipe fish), and ganoidei; 3, plagiostomi, with or- ders holocephali (chimsera), plagiostomi (sharks and rays), and protopteri (lepidosiren). Prof. Huxley places fishes in the lowest of his three great divisions of vertebrates, the ichthyopsi- da, including also the batrachians, from the possession of gills, either permanent or tempo- rary ; hence he calls them also branchiate ver- tebrates. He divides the class pieces into six orders : 1, pharyngobranchii (amphioxus) ; 2, marsipobranchii (lampreys and hags) ; 3, tele- ostei, ordinary fishes ; 4, ganoidei ; 5, elasmo- branchii, sharks and rays; 6, dipnoi (lepido- siren). A new classification was published by Prof. Agassiz in his " Essay on Classifica- tion," p. 187 (1857), the result of the systems of Cuvier and Muller and of his own scale method, with additional light from his exten- sive anatomical and embryological researches. He divides the old. class of fishes into four; his 1st and lowest class is myzonts, with two orders, myxinoids and cyclostomes ; 2d, fishes proper, with two orders, ctenoids and cycloids ; 3d, ganoids, with three orders, ccelacanths, acipenseroids, and sauroids, and doubtful, the siluroids, plectognaths, and lophobranchs ; he was then doubtful whether this class should be separated from ordinary fishes ; and 4th, sela- chians, with three orders, chimarai, galeodes, and batides. These classes he regards as equiv- alent to amphibians, reptiles, birds, and mam-