PISCES. . 203 
Plagiostomes of authors fall under this order. The families are: Rajacei, 
Cestraciones, Hybodontes, Squalini, Chimera, Ichthyodorulithes. 
II. Ganoiws. Here the scales are bony and covered externally with 
enamel, generally angular and continuous. Most Ganoids are extinct ; 
the most striking and typical recent representation is the Lepidosteus or 
gar-fish. Families: Sturionini, Lophobranchii, Gymnodontes, Sclerodermi, 
Cephalaspides, Pycnodontes, Celacanthi, Sauroidei, Lepidosteini. 
Ill. Crenoms. This order corresponds nearly to the Acanthopterygii 
of Cuvier. It is characterized by the roughness of the scales, the border 
of which is generally dentated, and by the usual presence of spinous rays 
in the dorsal and anal fins. Families: Mugiloidei, Aulostomi, Pleuro- 
nectidel, Squamipennes, Theutyes, Gobioidei, Scie@noidei, Sparoidei, Per- 
coidet. 
IV. Cyctomws. These are represented by the greater number of the 
Malacopterygii of Cuvier. The scales are generally smooth, and not 
dentated. The dorsal and anal fins have generally soft rays. Fami- 
lies: Anguilliformes, Halecoidei, Esocini, Cyprinodontes, Cyprini, Lab- 
roidet, Lophioidet, Blennioidet, Sphyrenoidet, Xiphioidei, Scomberoidet. 
The most recent classification of fishes is that of Prof. J. Miller (Ueber 
den Bau und die Grenzen der Ganoiden u. tiber das natiirliche System 
der Fische. 1846). We append a brief summary of this system as modi- 
fied by several authors. 
Orver I. Dermoptert. 
Internal skeleton unossified: external skeleton and vertical fins mucous, 
naked. Shape vermiform, or without any lateral fins. No pancreas nor 
air-bladder. 
Sub-order 1. Pharyngobranchit. 
Amphioxide. 
Sub-order 2. Marsipobranchit. 
Myxinoidei. Petromyzontide. 
Orper IJ. Mauacoptert. 
Internal skeleton ossified. Scales of the external skeleton mostly cycloid, 
in some ganoid. Fins all supported by rays, all of these jointed excepting 
sometimes the first in the dorsal and pectoral; abdominal or apodal. Gills 
free, operculate. A swimming bladder and air duct. 
Sub-order 1. Apodes. 
Symbranchide. Murenide. Gymnotide. 
Sub-order 2. Abdominales. 
Clupeide. Galaxide. Cyprinodontide. 
Salmonide. Esocide. Cyprinide. 
Scopelide. Mormyride. Siluride. 
Characini. Hypsocide. 
407 
