REPORT OX ZOOLOGY. 179 



4. Pisces. — It is generally allowed that this class is connocted 

 by close affinity with those Batrachian Reptiles which have 

 permanent gills. That it also leads back to the Mammalia by 

 means of the viviparous sharks, which approach the cetaceous 

 animals, will scarcely be doubted by any who have considered 

 the relative organizations of these last groups. Yet no one ap- 

 pears to have thought of placing the Fish between the Mamma- 

 lia and Amphibia before Mr. MacLeay, whose circular arrange- 

 ment of the classes of Vertebrata is certainly the only one yet 

 given that conforms itself to nature. As a class, the Fish have 

 received but comparatively fittle attention from naturalists ; and 

 from the time of the appearance of the first edition of the M^gne 

 Animal of Cuvier, to that of the Hist. Nat. ties Poissons by the 

 same illustrious author, but few attempts have been made by 

 other individuals to elucidate their true affinities. Several works 

 of great merit, descriptive of the fish of different countries have 

 appeared, and many detached memoirs on particular genera and 

 species, but no work of a regvUar systematic character since that 

 of Lacepede. 



Cuvier's system, as developed in the first edition of the JR^gne 

 Animal, is very different from that of Lacepede, which he objects 

 to as having all the secondary groups established upon charac- 

 ters drawn from the presence or absence of the opercle and 

 branchiostegous rays, which Cuvier observes will often lead to 

 glaring violations of natural affinity, not to mention the circum- 

 stance that in many instances Lacepede has assumed these parts 

 to be wanting where they are really present. Cuvier adopts as 

 primary divisions the two groups of Cartilaginous and Osseous 

 Fishes, commencing with the former, which he divides into the 

 two orders of Chondrojjteri/giens a branchies fixes and Chondro- 

 pterygiens a branchies libres. The osseous fishes he divides into 

 six orders. The first of these, Plectognathe^, is characterized 

 by a peculiar mode of articulation of the jaws, and comprises 

 some of the genera before included in the old order of Branchi- 

 ostegi, which is here abolished. The second, hophobranches, is 

 founded upon a peculiar form of the gills, and includes but the 

 two genera Syngnathus and Pegasus of Linnaeus. The remain- 

 ing orders comprise the Malacopterygii and Acanthopterygii of 

 Artedi, the former group being divided into three orders ac- 

 cording to the position of the ventrals, the latter kept entire as 

 one order. 



Blainville's arrangement of this class * does not differ materially 

 from that of Gmelin, excepting that the leading groups have 

 new names affixed to them, and new distinguishing characters. 

 * Priiiclpes, S)C., tab. 6. 



