ARTIFICIAL KEY TO THE FAMILIES OF THE TRUE 

 FISHES OR TELEOSTEI. 



The following key is intended simply to facilitate the identification of 

 species of the true fishes. No attempt is made to indicate the natural 

 characters or relations of the families, and only those species of any group 

 which are included in the present work are taken into consideration. 

 Most of the ordinary fishes can be readily placed by its means, but it 

 should not be trusted in the study of ichthyological rarities, or of fishes 

 from the deep seas. 



I. VENTRAL FINS PRESENT, ABDOMINAL. 



A. Back with an adipose fin behind the single rayed dorsal fin. 



B. Adipose fin composed of a single spine with a thin membrane ; 



body mailed XXXV, LORICARIID.E, 155. 



BB. Adipose fin without spine. 



C. Head with 4 to 8 long barbels about the mouth and nostrils ; 



body scaleless; a single spine in each pectoral and in 



dorsalfin XXXIV, SILURIDJC, 115. 



CC. Head without barbels as described above. 



D. Sides of body without photophores or luminous glands; no bar- 



bel at throat. 



E. Body scaleless; teeth very strong, some of them fang-like. 



F. Dorsal fin very long and high, occupying nearly whole length of 



back LXXXI, ALEPISAURID.E, 593. 



FF. Dorsal fin short, median or posterior. 



LXXXII, ODONTOSTOMATID^E, 597. 

 EE. Body scaly. 



G. Pseudobranchiae present. 



H. Dorsal, anal, and ventrals each with a small but distinct spine ; 



scales ctenoid CIV, PERCOPSHXE, 783. 



HH. Dorsal, anal and ventral without distinct spine. 

 I. Head naked. 

 J. Branchiostegals 6 to 20. 

 K. Dorsal fin long and high, of about 24 rays. 



LXV, THYMALLIDyK, 17. 



KK. Dorsal fin moderate, of fewer than 20 rays. 

 L. Stomach with many pyloric cceca. 



LXIV, SALMONID^E, 460. 

 LL. Stomach with few pyloric caeca; size small. 



LXVI, ARGENTINID^fl, 519. 



JJ. Branchiostegals 3 or 4 ; mouth very small. 



LXVII, MICROSTOMATID^, 527. 

 II. Head scaly on sides. 

 M. Maxillary very narrow, rudimentary, or obsolete; hypocoracoids 



not divergent LXVIII, SYNODONTID^E, 532. 



MM. Maxillary well developed, dilated behind; pectorals normal; 

 hypocoracoids mostly divergent . LXIX, AULOPODID^E, 541. 

 GG. Pseudobranchise absent. 

 N. Pectorals normally formed, teeth incisor-like or else rudimentary; 



pseudobranchise absent XXXIX, CHARACINID^E, 331. 



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